SDiver - Good advice, especially the part about staying close to the bottom in shallow(er) water. Course the last time I swam >1 mile underwater it wasn't with recreational gear either. (Yes - I'm jerking your chain
) I quit doing MILSPEC nav swims a long time ago. My preferred method for an extended surface swim is to shoot an azimuth, convert to a reciprocal heading, roll over on my back, put the compass on my chest, and read the heading through the sight glass/window. All your other steps are the same.
MW - I'll be checking out the Suunto too. Personally I use SCUBAPRO and Aqualung wrist compasses and don't have the problems with them that many people do with console mounted compasses. That and the "swim backwards" technique isn't as susceptible to needle/card lock. NTM I HATE snorkels and will avoid using them whenever possible. FWIW - Peregrino