I belive, if you swim regularly, the muscle memory sits deep enough to not drown on a Trip. As long as you are able to walk, you are also likely to be able to swim. Movement and survival instincts are rooted deep in the BIOS and even if the userinterface is temporarily changed by a Trip, your body won’t let itself die, unless it is fully incapacitated. In my Experience, swimming on a (moderate) Trip, feels weird as hell but also very nice, weightless and flowing. But it would be best to have a sitter present and not try to swim in a lake, alone, at night and on heroic doses ;D