There are several rock strata on the Western shore, any one of which could continue underwater.
Hopefully this pic may help identify the one that does.
There is also the beginning of a cairn with a piece of drainpipe sticking out of the top on the west shore to help mark the spot.
Note that the rockface you are interested in is the one with a dip in it's upper profile, unlike the one below, which looks equally promising at high tide.
