We actually moved to this anchorage from St.Marys Pool when the wind shifted. Remarkably there was only one other boat there and we essentially had the entire place to ourselves.

The water was crystal clear and mostly sandy bottom with patches of eel grass dotted around.

At low spring tide we had just under two meters beneath our keel (1.52m draft). A short dingy ride gets you over to a small ferry stop on the south side of Tresco with great walks no matter which way you turn. 
 

The swimming was amazing in the glass clear water, but beware, when the tide starts to run it accelerates at a pinch point near the rocks as the channel narrows and can become overwhelming quite quickly. Ask us how we know?