The main pool is 33 metres long.
The width is unknown, but it must be at least a third of the length, which I would consider is big enough for even the largest of boats. (I've seen them practicing canoeing in that pool!)
There is a smaller practice/learning pool, next to the main pool. This is much cheaper to hire than the main pool, and will likely be the only financially viable alternative, if we don't get at least 20-30 submariners show up.
Main pool hire is about £60-70 per hour, and a large slice of that is for the lifeguard, which unfortunately you can't option out!
For three hours then we're looking at £180-210...ouch!
With a bit of arm twisting, perhaps I could get this knocked down a bit, but probably not by much.
Assuming I could hire the facilities for £150, then we'd still need a minimum of 30 submariners paying £5 per head to just break even!
The smaller pool is about £60 for the whole evening, a lot cheaper, but the pool is much smaller, therefore I don't think it'll have the same draw as the main pool.