In reply to harry 600: Some pools have kayak sessions. Rowing though? Even 50m is a bit short. Climbing walls are climbing gyms for climbers.
Mountaineers? I'd rather go outside, that's my training.
I don't think you've thought this through, the best thing to do would be to add some exercise machines to an existing climbing wall to diversify training. In my experience people go climbing for training for climbing, not many people I know will go to a gym to train for it.
Plymouth's life center is a huge sports center that will run kayak sessions, has a climbing wall and a large gym/pool.
> pool's for kayaking/rowing, training walls. lots
If it's in an area where those facilities don't already exist in one form or another and there is demand and you could make it attractive... Maybe. That's assuming you could afford it and make it pay and somehow survive the winters when people will mostly be going indoors.