Rick Inman:So, what is the depth one of these cruse ships lays at? How deep would you have to be to be assured it would pass over you??
From the pictures I saw of the cruise ship in question, it looks like one of those new jobs and probably has a draft of about 25-30' or thereabouts. And at that it won't do you that much good if it passes over you and also sucks you up into the propellors, so you have a lot to worry about even below 30'. The more confined the water around the ship (i.e., to the extent the water is shallower and also bounded vertically by reef or other structures), the greater the draw of those propellors.
On edit: Unless you're on the *other side* of a reef or other vertical barrier, of course, in which case you are a lot better off.