How can I tell that my bottom paint needs repainting

[Boasun]

That is why you go to the sporting goods store and get yourself a mask & flippers. To inspect their work.

Its only water! You won't melt or desolve away.

[capttb]

Just so happens I've a dockmate who has an underwater video camera which works real well for checking the bottom. I may not melt but I'm too old to enjoy a dip in cold water anymore. "Waterlining" is rumored to occur at times, cleaning bottoms can be a REALLY difficult thing to do day after day, year round.