As the one who wrote the recommendation that ultimately put those GFCIs (it Interrupts the Circuit, the Ground Fault still exists) in your bathrooms, kitchens, and on your patios, I can tell you that if you are tripping one, you need to find out why! To ignore it is like putting a bandaid on a melanoma. The GFCI detects a leakage in the system by monitoring the differential current in the legs of the circuit, and trips at levels (current and time) below what would normally be fatal to a human who happened to get between that leakage and ground.
I can't speak as an expert on this since I have no experience with it, but I do not believe reverse polarity will trip one. It appears to me that the same differential will exist and I do not believe it carries a sign since by definition the sign on a sine wave is changing 60 times a second anyway. However, a GFCI tester may not work on a circuit with reverse polarity due to the way they simulate the ground fault. This could lead one to replace a GFCI which is actually working properly. The only fool proof test is the test button on the device itself.
Believe it or not, one compelling reason for the invention of the device was unexplained deaths during ECGs in doctors offices. Those leads are right across one's chest, and a leakage can (and did occasionally) cause the heart to stop (dead!). It doesn't take much. Someone asked the right questions of the right people.
I would suggest that if your boat is tripping a GFCI at a given marina, there are two possibilities. That marina's are overly sensitive (not likely) or the other marina's are not sensitive enough. Given the choice, I prefer one that is more likely to keep me from electrocution rather than one less likely to do so. You need to find out which is the case before someone becomes a path to ground.
If just disconnecting one's boat from power saves its zincs, the problem is on that boat and should be found and repaired. But that is probably an entirely different problem.
