I'm just pasting what I wrote in another thread, it might be useful here:
This works well on a calm sea but not so well with a pitching deck.
In this case, you can use the F4 camera and Rctrl+Rshit+Numpad keys to move the camera around.
It's slow and the view wont be saved if you switch to another camera but it allows for precise camera placement and, assuming your aircrat is parked on the deck, the camera will be synced with the pitching deck.
note: in order to move the F4 camera with the numpad keys, you need to be spawned in an aircraft, it wont work if you are a spectator.