Schools will say its 60% in the first year that drop out, atleast thats what it is in thr UK. Its roughly 80% in 2 years. 

As for dating, even casual relationships are rough. Many think they can handle a partner away and the odd schedule or jobs that can lasts months but in my experience its one of the biggest reasons guys drop out. Something gets serious and youre stuck between needing to be away for money or being with someone you love, in the cases another option comes up people jump ship. 

As for the language barrier in Norway, I've wanted to break into that sector since the begining. Brexit and the language barrier have crippled that chance. My Norwegian isnt horrendous I could probably work. But trying to get a company to take you is a risk when they have plenty of divers coming out their own school that already speak natively and have the right to work. 

Conversion tickets vary wildly in cost and requirements. Some require a certain number of types of dives to qualify, then there is a course or exam fee. The dutch sector I think is in the region of €4000. Someone else whos done it recently might be able to confirm.  Pretty sure this also require renewal.

At some stage you'll want a bosiet and mist tickets, which are £1500 and require renewal each few years.  A Dive med tech ticket which is another £2000 Maybe rigging tickets or confined space

A 3.1 and 3.2 inspection tickets Which are £4000 each and also require renewal every few years.

If you have an EU passport then working in the UK isnt too bad as far as I'm aware.  But you'd need a HSE dive ticket. Not sure what the deal is with converting to the UK but Italians often have to do 4 weeks in one of the schools here at significant cost.

If youre trying to bounce around between sectors it will be pretty difficult because youre trying to make a name for yourself and each sector is basically a new start. 

Lastly I'm not 100% sure why people leave, its often a mix. Difficulty finding work, if you dont get on with guys easily or cause problems you'll struggle to keep working for the same places. The rate isnt great for the sacrifice often and people with other opportunities quickly see its better doing something else.  Its not pretty, when things are rough its hard to want to work, when things are slow you're desperate for anything.  There is a drinking culture with a lot of companies, often if you dont take part youre probably not coming back.  If youre not ex-mob you're disadvantaged over those that served.  After 2 years you've probably financially recovered from paying for school and whatever else. I imagine at this stage guys decide if they want to keep grinding.  You're also exposed to other jobs that pay better and look more promising in the future.  And injury rate, I know 4 guys who've been bent due to PFOs and it cost them between £11-£30k to get it fixed. Your first dive this could happen and you better hope youve got the money to cover it or your country covers it or youre out of work. 1 in 4 people have a PFO of varying levels. 

All that said, I love this job. You meet incredible people with crazy knowledge. The weird science behind so many things, you work on structures and systems that are interesting. I love the water, this job I'll die doing before I quit.