If it's your first flight over a significant body of water then there's another thing you need to be aware of. Perfect VMC weather (CAVOK) is almost like IMC over water, as the grey-blue of the water melts seamlessly into the blue-grey of the sky. So you see absolutely no horizon in front.
Solution is to go on instruments, flip on the autopilot, or look straight down at the water and the shipping to keep oriented with the right way up. Up to a point you may also be able to see a horizon on the sides of the aircraft, or behind you.
It's not necessarily dangerous, it's just something you have to think about a little in advance.