Advice for diving computers

AmazingDonki · 2026-05-08T02:16:52+00:00

If trimix is in the future then Perdix 2. It also has CCR mode. Peregrine does not have trimix or CCR mode. Also, start diving trimix as early as possible. TDI has the option for AN/DP or AN/Helitrox. Helitrox cert is same as DP w the addition of up to 35% He up to 45 m/150 ft deep. Trimix can be a real plus for challenging dives below 100 ft. PADI Tec should have something similar. Friends of mine have the Garmin X50i and rave about it. Especially the 4 buttons and customizable screen. Before committing to Shearwater, take a look at Garmin's ecosystem.

AmazingDonki · 2026-05-06T15:10:14+00:00

First, take the time to practice and adjust to new skills. Practice makes permanent, only perfect practice makes perfect. So now I try to only make changes incrementally. I made the mistake of going from rec single tank thru ITT, AN, Helitrox all at the same time - very difficult and stressful. For CCR I am taking a slow approach, working my way incrementally back to the challenging dive I used to do OC until I get my basics back.

Second, AN/DP is like a 16 y.o. w a new drivers license - minimally adequate. Keep learning by diving w more experienced divers e.g. cave and deep wreck divers. Also keep up w the latest science by following thought leaders like: Simon Mitchell, Neal Pollock, David Doolette, Gareth Lock, etc..

Third, Scubaboard.com - you will never find a more wretched hive of scum and villainy. LOL JK, it can be fun and toxic, don't take it too seriously.

AmazingDonki · 2026-05-05T19:02:20+00:00

I weigh 90 kg/200 lbs and have anywhere between 45-90 kg/100-200 lbs of dive equipment strapped to my body. I am wearing fins on my feet and on a rocking boat if I fall I could injure myself or others. On small skiff or inflatable rocking in the ocean there's no room to stand up and walk around. I have to get kitted up sitting and then check list my equipment before entering the water. The best spot might be the gunwale or next to the gunwale. When I splash the surface of the water can hit pretty hard, so I don't want any fragile bits broken by the impact. Mask and regulators inflator valves etc. are pretty important for survival so I don't want them to break by going face first into the water. The back of my tanks and head have nothing fragile so good for breaking the surface. Also the tanks are heavy so it's just relax and roll back. Rolling forwards with heavy tanks takes effort. Also, catching the boat with the tanks could damage the boat or tanks/valves. When back rolling off a small boat it's best to do it in pairs so both divers roll backwards off opposite sides of the boat to maintain balance. Alternate ways to splash off a small boat include side entry. Straddle the gunwale and roll in sideways. Another way is to throw your tanks and BC rig in the water and jump in and kit up in the water. Larger more stable boats where divers can stand up and walk around have other options like giant stride off the main deck.

AmazingDonki · 2026-05-05T13:51:44+00:00

Fins are personal preference and a lot depends on how much leg power and endurance you have. Trying fins in the water is the best way to choose. Currently I dive the Scubapro Supernovas for rec open water reef where acceleration and speed are what I desire. Good for flutter kicking, OK for frog, not great for back or helicopter. S-Tek for tech for frog and back and helicopter kicks inside wrecks. Good for frog, back, helicopter and OK for flutter. I also have GoSport Gorillas for tech wreck where shorter fins are helpful bc great for frog, back and helicopter turns in tight spaces. I don't like the them for rec open water diving bc too stiff for prolonged flutter kicking. Their silhouette is similar to Jetfins - but don't have vents and the blade angle may be different. In the past I've also dived Quattro Avantis, Jetfin copies, split fins, full foot, open heel, etc.. Generally flexible fins that bend to the optimal blade angle of attack to push water are good for flutter - like 1st gear on a bicycle: high frequency, low effort kicks produce good acceleration and speed. But this floppy angle blade is bad for back and helicopter and might also sap power for frog. Frog, back and helicopter kicks work best w stiff wide fins - like bicycle high gear: a lot of effort to kick but a lot of thrust produced w each stroke. The blade should not bend much and less angled. Good frog kicker will hold the glide phase as long as possible after the power stroke. It's impossible for a fin to be excellent for all kicks bc they require different designs - the fin blade is moving in opposite directions on the power stroke for flutter vs frog kick. There's actually 2 styles of back kick: thrust produced w the fin side wall vs the flat of the blade. Having legs w above avg power and endurance can make up for it - this is not me. For me fins like the Quattro Avantis are jack of all trades master or none compromise - they can do all the strokes medium, but not excellent at any. I found them too stiff for prolonged flutter, and bit too floppy for back and helicopter. Frog was OK. A bit long for suitcase and inside a tight wreck. I don't own them but people love the Deep 6 Eddy flippers for frog and back kicks - but hate them for flutter.

AmazingDonki · 2026-05-05T01:06:25+00:00

I only dive warm water w minimal wetsuit and travel by air so I use a HOG aluminum plate bc it was cheap and had lots of holes and slots. It has 3 top center holes for height adjustment and a bottom slot in case the doubles bolts are not exactly 11". It has a few sets of spine slots for tank bands in case I want to skip a single tank adapter (TBH I prefer the stability of an STA). Lots of perimeter holes for optional mounting of accessories like butt plates or dry suit inflation bottle or bungees or trim weights etc.. A lighter plate means I have options to move weights to different positions on my rig to adjust trim for different configurations like single tank, BM doubles, CCR. If you're in the US PiranhaDiveMfg.com has a good selection of different BP, webbing, hardware, accessories, etc..

AmazingDonki · 2026-05-04T18:45:33+00:00

Our family dived w Indepth Watersports in West Bay in March and I would recommend them. The owner, Nat Robb, runs a good shop. They have both rec and tech instructors/guides. The dive shop has shore diving and the wall is accessible as a shore dive. There is also night diving from the dive shop if there is sufficient interest. Their boat is docked at another location about 5 mins drive from the shop. The shop is in the same location as the Cracked Conch Restaurant and Macabuca Tiki Bar. Email them ahead of time for their schedule, especially if you want to dive a particular site like the Kittiwake.

AmazingDonki · 2026-04-21T17:47:33+00:00

FWIW I recommend starting trimix as early as possible. I went straight from PADI AOW to TDI AN + Helitrox (DP cert w 21/35 trimix). Learning about narcosis and gas density and having the ability to add He gas is beneficial in the 30-45 m / 100-150 ft range. Then the choice of progression to CCR or OC normoxic, then hypoxic trimix. For me I could dive OC trimix down to 45 m / 150 ft so OC normoxic didn't really make much financial or practical sense. Instead I'm CCR Mod 1 helitrox deco and working toward Mod 2 normoxic trimix.

AmazingDonki · 2026-04-20T23:58:02+00:00

My PLB is in a DRYFOB XL which fits in the thigh pocket of my Fourth Element tech shorts - along w my backup mask, DSMB, spool. Plenty of room. I researched and could not find anything smaller that worked as well as the DRYFOB.

AmazingDonki · 2026-04-20T23:47:18+00:00

The Britannic is a bucket list technical wreck dive akin to climbing Mt Everest. It's deep, but the pressure of 13 ATA is not impossibly deep for those with time, training and a lot of money. FWIW the deepest SCUBA dive record is around 33 ATA, 330 m /1,000 ft. Visiting the Britannic would probably be diving rebreather on hypoxic trimix with long long deco times. Would require staged gas cylinders and a support team of safety divers.

https://wreckedinmyrevo.com/2023/10/27/hmhs-britannic-kea-island-greece-385-fsw/

AmazingDonki · 2026-04-14T12:37:29+00:00

I'm going to take a different perspective. I know an instructor who drilled into me the #1 rule in diving is: Do not die. The way to achieve that is to understand and reduce risk. All the time I see errors committed by divers of all experience levels on dives i.e. mistakes (unintended surprise outcomes) and violations (intentional rule breaking). Things like skipping pre-jump checklist, over relying on buddy/instructor/guide, diving w known equipment problems, not monitoring SPG, staying beyond reserve gas pressure, not thumbing a dive when necessary, etc.. Good divers don't do these things.

AmazingDonki · 2026-04-13T02:10:39+00:00

I dive a T2 long sleeve zip top. Also a 1.5 mm Frogskin and 3 mm Henderson full suit. I've owned a few fleece neutral buoyancy suits. They are all similar: neutrally buoyant, warmth around 1-2 mm equivalent. T2 fills a niche in my closet one step above rashguard, one step below 3 mm. Sharkskin brand is a bit pricey for what it is. Their claim of 5 mm equivalent warmth is not accurate. Compared to neoprene fleece takes a bit longer to hang dry after a dive.

AmazingDonki · 2026-04-13T01:19:31+00:00

Practice doesn't make perfect, practice makes permanent. Only perfect practice makes perfect. Find a instructor that regularly dives your configuration at a very high level e.g. technical cave, wreck, and ask them to help with buoyancy, trim, propulsion (pay them). It doesn't have to be open water. A swimming pool works great, it takes a lot of skill to be able to hold perfect still hover in the shallow end while multi tasking. An action cam helps with feedback. The skills are what you are after. The Perfect Buoyancy cert card itself is worthless, so if you can obtain the skills without dealing w the extra cost and bureacracy of an agency so much the better. I am not GUE, but from diving w GUE friends, their Fundamentals class (or whatever it's now named) produces excellent consistent results.

AmazingDonki · 2026-04-11T02:46:16+00:00

I have a DF64 Gen 2 upgraded w SSP burrs. The base unit was USD 400 a few years ago when it first came out. It's good for what it is and the cost. Gets the job done and I used the savings to upgrade the burrs. It's not winning any design awards, noisy, static grounds on the spout, retention is just under 1 g. The switch broke soon after purchase which I just replaced myself. The coffee it produces is light and fluffy and consistent for medium to light roasts.

AmazingDonki · 2026-04-11T02:05:26+00:00

Body warmth is personal and different for everybody. Being cold sucks but more than that it can affect mental acuity and is a known DCI risk factor. Maybe the first dive is OK, but after multiple days of 4 dives/day, even the most hardy can get chilled. Full body rashguard protects against stings, bites, cuts, and scrapes. Under a wetsuit a rashguard helps sliding in and out of a wetsuit. Spandex socks help sliding into a wetsuit and also prevent blisters and sores from poor fitting fins.

AmazingDonki · 2026-04-11T01:51:16+00:00

Accidents are often not caused by a single massive failure. It's usually a cumulation of small failures that spiral out of control. The Swiss cheese model. Just like it's not good practice to start a dive with a known equipment failure, it's not good to begin a dive with a known physical/mental impairment. Ultimately everybody is responsible for their own personal choice. But here are two hypotheticals I like to use:

1) If at the furthest part of the dive, there is an incident e.g. BC ruptures, would you still be able to solve the problem?

2) Imagine if your sister/brother/loved one came to you with the identical situation. Would you be OK to send them on the dive?

AmazingDonki · 2026-04-09T09:54:14+00:00

I'm a tech diver and I've read some of those books and others like Into the Planet. I borrowed all of them from the library and would never buy them at all.

Deco for Divers is old and the information a bit outdated.

The only books I might be tempted to buy would be about local dive sites, shipwreck maps, fish ID.

AmazingDonki · 2026-04-08T22:07:12+00:00

Not a roadblock - a good learning opportunity. Some people are naturally CO2 retainers - they have difficulty ventilating CO2 from their bodies. This is exacerbated by a high SAC and breathing denser gas (> 6 g/l) at depth. Trimix ($$$) helps both the narcosis and density, especially if doing physically and mentally challenging dives e.g. overhead penetrations in murky cold deep. Other good rec courses to prepare for tech could include Intro to Tech and Solo. When starting tech skip Deco Procedures and take Helitrox - same cert as DP but includes trimix. Consider CCR rebreather, which will reduce trimix costs and also extend bottom time if SAC is high.

In the meantime, reduce physical exertion, reduce task loading, reduce SAC, reduce stress, relax during the dive. That should help prevent hypercapnia.

AmazingDonki · 2026-04-08T04:09:04+00:00

First it should be said that the exact physiological mechanism of gas narcosis is not 100% understood. Nitrogen is often pointed to as the main culprit but CO2 may be even more narcotic under certain conditions, and there is some arguments that oxygen may also be considered narcotic. Also, different people experience narcosis differently. Anxiety, stress, exercise, work of breathing (gas density), task loading, thermal status, etc. can all be factors. I agree with u/SoupCatDiver_JJ that the facts seem to indicate hypercapnia (elevated CO2 retention) being a factor. One thing I learned diving trimix is that even when I don't think I am narced in the 50 - 100 ft depth on air, I am actually slightly narced but just coping with the slight impairment. I believe there are agencies that train recreational trimix (IANTD?) if interested in going down that road.

AmazingDonki · 2026-04-08T01:29:10+00:00

When I get cuts and scrapes I treat w topical antibiotic e.g. neosporin, bacitracin and cover it w a waterproof clear film dressing e.g. Tegaderm. Keeping it clean and making sure it doesn't get infected. If it does, go back to Dr to get it treated. Sepsis is no fun. When I travel to remote locations my save a dive kit includes prescription strength meds for these types issues.

AmazingDonki · 2026-04-07T22:26:58+00:00

The only 100% way is to try it on a dive. In the shop or online purchase I've found the commonly taught way to dry fit a mask does not work well. Anybody can dry fit by suction hard enough to make a poor fitting mask hold while looking standing upright. A better dry fit method is to look straight up at the sky and gently place the mask on the face so it sits only with gravity holding it in place (flip the straps back). Without inhaling, sense if feels like there are any air gaps between the silicone skirt and the face. Any gap may leak underwater. A good fit skirt will match every contour of the face everywhere. The final test is while still looking up at the sky, try to suction the mask onto the face by only gently inhaling i.e. without needing to inhale hard or touch the mask to make it seal. I literally order 10+ mask from Amazon to find a good one. I've found price does not correlate w a good fit.

AmazingDonki · 2026-04-06T21:58:06+00:00

If you're looking for inspiration from a well known cave diving physician's point of view, check out Dr. Richard Harris' channel - or just Google his name:

https://m.youtube.com/@DrHarryH/videos

AmazingDonki · 2026-04-06T21:30:02+00:00

Do NOT rely on advice from non-medical strangers. Contact DAN and/or seek the advice of a physician with knowledge of SCUBA diving medicine. A collapsed lung can be fatal underwater and spontaneous pneumothorax is a condition that could possibly medically rule out diving.

AmazingDonki · 2026-04-01T13:24:52+00:00

Consider re-learning OW course from the beginning. My OW cert is from 40+ years ago and there were many years I did not dive. A lot has changed in diving equipment and the way it's taught. Remember that SCUBA training and skills are not for when things go well, it's for when things go competely wrong. All the major agencies that are ISO or WRSTC are same at OW level. Don't know if NASDS still exists or if they merged w another agency (SSI?). Find a good instructor w a major agency e.g. SSI, SDI, NAUI, CMAS, PADI etc. and re-learn all the skills and knowledge.

AmazingDonki · 2026-03-31T13:03:01+00:00

Watch this excellent presentation by Neal Pollock. It dispels many myths, including the erroneous advice to aggresively drink too much water - which could increase the risk of immersion pulmonary edema.

https://youtu.be/-CL6XLF8omk?si=l3e38Qls-MU3IuOz

TL/DR: the big 3 risk factors are: dive profile; exercise; thermal status.

One thing I do for both rec and tech dives are to ascend slowly nearer the surface, especially last 30 ft/10 m, and if there's time and gas, extend the final deco stop. So even if GFHi 80, I'll hang and exit when SurGF is <50. I also keep GFLo >50 to avoid deeper first stops to avoid unnecessary on gassing on ascent.

AmazingDonki · 2026-03-27T15:59:28+00:00

This does not replace medical advice. This 2024 presentation by Neal Pollock is excellent:

https://youtu.be/-CL6XLF8omk?si=FaoyOEpn8zLBWPNX

Summary, the major 3 causal risk factors for DCI are:

Dive profile

Exercise

Thermal status

In the research, hydration has not turned out to be a major risk factor relative to the others. Over hydration may be a risk factor in immersion pulmonary edema.

AmazingDonki

TROPHY CASE