There were a number of these guys of varying sizes and inhabiting a variety of seashells. These 3 individuals were in the same area at the same time of this spotting. The 1st, and smallest, was in a small conch shell and I believe it was sizing up a Four-toothed Nerite. The 2nd, larger one, in a Tulip's shell was intent on scaling a grate that blocks the lagoon opening to the ocean. The last and largest was moving along the sea floor in the shell of a Crown Conch.
A small flock of nonbreeding adults was foraging on the exposed rocky seabed during low tide. One of them (see pic 2 ) was missing a leg.
This lone Immature or female was fishing in the early morning.