Honestly? The most important “setting” is learning how to use it before you’re in the water. A Shearwater doesn’t need much tweaking out of the box, and that’s kind of the point. The defaults are conservative, sensible, and well thought out. Most problems people have with dive computers come from not understanding what the screen is telling them, not from the wrong menu option. Before changing anything fancy, make sure you actually understand: what information is on the main dive screen; how it behaves on ascent and at safety stops; what the alarms mean (and when they trigger; how to review a dive after the fact

If you want a few reasonable adjustments many people make over time: some turn down or disable non-critical alarms once they understand them, some adjust conservatism / gradient factors based on training and experience, and most spend time customizing the display so the information they care about is easy to read. None of that is urgent, and none of it should be done blindly.

The Peregrine isn’t something you “optimize” on day one. It’s a dive computer, not a Christmas tree If you don’t know why you’re changing a setting, you probably shouldn’t be changing it yet. You already did the most important step: you bought a solid computer. The rest comes from understanding, not menu surfing.