Reelapeelin is right on the money (again)... The Hull cleaner is the best stuff out there. It's made by Marykate and it's called On and Off. It will work instantly not only for bug poop but also for just about anything you can throw at it....hull scum, tar, barnacles, you name it. It's powerful stuff, but it works like nothing else and WILL NOT harm your fiberglass. I use it all the time.

A word of caution!!!! This stuff is NASTY on your skin and even WORSE on your eyes.. FULL GOGGLES ARE A MUST when using it, as well as the aforementioned gloves for your hands.

What makes it so powerful is:

Hydrochloric Acid

Rubber gloves, protective clothing and eye protection are essential.. and DO IT OUTSIDE... the fumes from this stuff are just as bad for your lungs as the stuff is for your eyes.