Hmmm. The only pro-snorkel position that seems to be getting any traction is hanging out or long swimming on a rough to very-rough surface.
Hanging out on calm surface: float head-up or on-back.
Long swimming on calm surface: float on back.
Does anyone have experiential or experimental data, in, let's say, >3 foot rolling seas or breakers of any height, with back-inflation or wings:
- long swimming: ability to maintain position on your back despite seas and breathe reasonably comfortably
- hanging out: ditto (back or upright)?