This video shows just how hard it is to spot someone in the water
. This was done from a stationary helicopter. Add forward flight from a fixed wing aircraft and it makes it even more difficult. This is why it is so important to make your searchers see you.
Chief Hathaway shows one method by throwing water
into the air. This is very effective when you have nothing else (signals).
He also shows how to preserve body heat by performing the Heat Escape Lessening Position (HELP). The only thing he didn't mention is that the HELP position CANNOT be held without wearing floatation.