O is for Oceans: Hitting the Trail with the Wilderness Survival Guide

Swimming (drowning) rules.

"Only characters with proficiency in swimming" can swim.

Rules are provided for encumbrance on swimming and its effect on endurance, speed, diving and surfacing.

Endurance (turns of swimming) = experience level + constitution score
Speed = base (40 feet / round humans, demihumans 30') modified by strength, current, above or below the surface.

Diving and surfacing base = 20' per round.

Other rules
Treading water (turns) = double endurance

No proficiency in swimming = tread water for strength score in rounds.

Breath holding - did this one in A (2011) Dungeoneers Survival Guide
1/3 Constitution in rounds


Not too bad.

Shipping (more boating) rules follow with capsizing rules depending on boat size and wind, portaging, movement modifications for large move (miles / day) and small move (feet / round) covering normal sail, max sail, normal oar and max oar.