Flush and empty the bladder and remove it. Make sure the hoses are capped tight. See if the smell goes away after a couple of days.
While Pure Arye might work, it can't get into places you can't spray, and doesn't permeate fabrics and cushions very well. It is also expensive.
Another way to remove odors is to use chlorine dioxide. This is a gas that does permeate fabrics and cushions, and finds its way into all nooks and crannies. It is an oxidizer that destroys odor molecules. You can make it yourself with sodium chlorite (cheap on Amazon) and an acid like muratic or citric that you probably have on hand, or can get cheaply at the hardware store. Put 5-10 Tbs of sodium chlorite in a bucket, add a cup or two of water, pour in 1/4 cup of acid and leave the boat sealed for 24hrs. In your case, probably just seal up the compartment with the stink with it. The mix will react to form a fog of chlorine dioxide that fills the volume of the area. If you have mold, it also will be killed. After, open up the boat for a while to let it all air out before going in.
What remains in the bucket is just table salt and water (possibly slightly acidic depending on the ratios added), so that can go overboard or disposed of on land without concern.
Mark