Good question indeed. Most of the time I operate my subs (Thor Alpha, Thor LA Phase II, Engel U-177 and (eventually) finished Engel Gato) at or near the surface. You can dive these boats all to about 1.8 meters. They all are equipped with a pressure mechanisim that electronically measures the water pressure and will not let you dive any deeper. Also, they all have electronic pitch mechanisims, which will keep the boat from porpoising, which is prevalent on the bigger subs. The really fun part (for me) is lurking just below the surface at periscope depth. To go any deeper you cannot see it (unless your water is exceptionally clean, I am not as fortunate) and therefore you will have to guesstimate where the boat actually is. Also, an important feature that I neglected to mention is a failsafe (or multiple failsafes in my case) It is important to incorporate a failsafe into your boat so that if Murphys law comes knocking you will at least be able to get your boat back. All radio systems will glitch occasionally underwater so a little is not bad, a lot is

Best regards,
Pete Olson (AKA Subsinker)

there are two types of ships: submarines and targets