Do this: M or this: * or this: @ or this: #
Basically there's no right or wrong way to "patrol". I basically do a pattern like this: /\/\/\/\/ across a grid and submerge at each end of a leg to check the hydrophones. If the pattern is large enough I'll submerge in the middle of each leg as well. Other times I'll do a spiral search. If I hear something on the hydrophones I'll move to intercept, if not, surface and continue on. Sometimes if I see a radio contact near me I'll abandon the pattern and move to intercept that.
One "cheaty" thing to help is not upgrading your hydrophone. The GHG one you start work works on the surface, so you'll catch a lot of contacts you'd otherwise miss due to distance or weather. Your call of ease of finding contacts vs realism.