We have anchored the dinghy at Eustacia reef many times, there are plenty of nice sandy areas.
There are two unmarked passes out of Eustacia sound, they are a few hundred yards apart.
Be careful of current and the occasional barge if snorkeling the reef near the passes.
We've also towed the dinghy while snorkeling. Not a bad idea to inflate the beach ball dive marker and attach to the dinghy to make the situation clear.
Tilting up the outboard can reduce the draft to a minimum.