Could be.
I immediately thought of the rocks I’ve seen at marinas to stop erosion. Those usually have some lights around.
This could have been on the open ocean near shore I suppose. In that case, you couldn’t see them could you.
You wouldn't see rocks or much else at that hour.
Very sad event, anyway. It seems like he was a young man with a lot of potential, both as an athlete and as a citizen.
This was reportedly Government Cut, a channel between South Beach and Fisher Island, long rock jetty, very choppy currents.