For the cost invested a scuba tank or two on a boat with a 50 foot hose in my opinion is your best entrance to being 'safely' equiped for any below the waterline boat maintenance. Yes I realize they need to be filled and that isn't always available but in many 'popular (read not necessarily in the remotest reaches of the world here)' areas there are hotel dive shops, and beach front dive shops, and dive boats anchored who can provide a quick fill. I have two tanks I keep under my bunk down below. If I need it I can pull it out and then refill it and put it back. A mask, weight belt, and regulator round out the picture. On occasion you even get to help others with rope on a prop or fixing something else under the boat. On that rare occasion when something falls from some ones boat in 50 feet you can even be the hero who throws on the scuba tank and rescues it. Of course that implies you have the other necessary gear in your locker for scuba.
If however you want to 'snorkle' away from the boat and can afford it then hookah does seem the way to go.
With all the other monetary hemmoraging I am doing though I just cannot afford the hookah. Be safe and have fun.
Boating isn't an attitude it is a way of life