Most cookers on hire boats run of bottled gas. If you're hiring a boat you can be fairly certain the hire company will have provided an adequate amount for whatever period of time you have hired the boat for.
The main difference between 'boat' gas and 'domestic' gas is that you should always turn boat gas off at night, or if you are leaving the boat for some time. In exceptionally hot weather this may cause problems with the contents of the fridge, but normally the fridge will be cool enough to last through the night.
In the unlikely event of a leak the gas, being heavier than air, will collect in the lowest parts of the boat. If you smell gas, turn it off at the cylinder and turn the engine off too.