I dont EXPECT satellites to be surveiling open water. I do know that they can be trained on any area necessary. The images can also be "studied" , not by eyeballs, but a simple software analysis could be looking for seat cushions. How hard would it be to dump some in the water & digitize the images & have software look for comparable images in the open water?
I know a guy whose brothers job it is to adjust satellites line of focus, so I know its something that gets done, they can "look" anywhere they want to look.,.,