Except when practising/training in a pool, scuba diving is done outdoors, and so would seem to fall under an "outdoors activity". Would questions on it therefore count as on-topic?
(I'm aware of the scuba diving Area51 proposal, and Travel.SE diving questions which tend to be more about where to go than how to do it. There's also a handful on the Sports beta, I'm just trying to work out if they'd also be on-topic here or not)