Haven't been on the forum in some time.. my apologies... maybe we need to change this to a facebook page? Anyhow, I'm probably the best person to answer this since I live in Deep Creek.
We call it the Gulley Hole. At low tide it is a separate blue hole, at high tide it is part of the creek. It is really quite pretty. Occasionally there are jelly fish that get trapped in there... they're the white ones that sting lightly. So, pay attention if you go swimming there. It's a nice spot to kayak.
To get there: Coming from Waterford... go thru Deep Creek, the road bends left at Sheryl's Inn and Restaurant. As it goes up the hill a bit you will see a 2 story business on the right and 2 story house on the left. (This is Trevor Pinder's Marine store and rental apartments - there are a lot of boats in the yard). There is a dirt road that goes alongside the 2 story house on the left. Take this dirt road. It's not very far that it dead ends at the Gulley Hole.