I don't know anything about satellite photography, but I've seen images like this many times on Google Earth. The image has a hazy, ghost-like appearance. My guess is there's some reason two or more digital images, taken at different times, have been combined. I've seen GE images of marinas with some boats appearing very faint and hazy, and even overlapping other images. It's usually in a transition area where two different images,clearly taken at different times, come together - near the boundaries of the different images.

In the Sandy Cay image there are areas where different images come together. One can see water with waves or ripples and completely flat water side by side, hazy clouds and crystal-clear skies separated by a perfectly straight edge. If you look just a few yards SW of the catamaran closest to Sandy Cay (and very clear in the photo) you can see what I think is the faint outline of a monohull (hardly visible). A few yards to the SE of the "clear" catamaran another catamaran that isn't visible initially can be seen as one zooms in closer. There are clouds obscuring it, but the clouds are in a perfectly straight line. There is an edge of another boat touching the catamaran on it's port, aft quarter. The edge piece is very clear. I think the edge piece is part of an image of another boat taken at a different time. I don't think there's a sunken catamaran at Sandy Cay, just the faint image of a catamaran that was captured in a photo at a different time and combined into the satellite view we are seeing.

There was an old dock with a Catalina 22 near my home marina that appeared on GE for a couple of years. The dock was destroyed by Hurricane Irene in 2011 (the Catalina was on the hard) and the dock was never rebuilt. In a GE image with an " imagery date" in 2014 the dock still showed up but it was very faint and hazy. It was in an area where two images came together that were clearly not taken on the same day. I know the dock was not there in 2014. As the GE images are pieced together these "ghost images" show up - at least that's my theory.