Being that you are looking for the waterproof and the immersion depth and time I would probably go with the reed switch if that is a viable option. Not sure what you need for current specifications, however something like HE557-ND for about $0.50.
If you look at a toggle I think the best I can do is EG4914-ND or push button EG4890-ND however you are up to $4-$5 + going that route. If you need some more help with specs please let me know.
-Robert