I used this product to seal the roof edge of my RV where it joined the side. I keep a roll for emergency use on boat. So far haven't needed it but I guarantee you it will seal any leak. Not sure it would be good where boat meets trailer bunks or is subjected to rubbing but it seals and holds underwater or above. Just make darn sure you have it where you want it because once you apply it, it is not coming off without a lot of scrapping and peeling and cussing.
EternaBond AlumiBond
Mark 1:17 ...I will make you fishers of men