The waters around St. Clement's Island, or should I say sand bars, can be very tricky for those not familiar with moving waters and their effects on the bottom. I watched three go fast day cruisers blast down river heading towards Breton Bay. They must've been mathematicians as the chose the shortest distance between two points and struck the bar between the island and Colton's Point instead of going around the island and getting in the shipping channel.
The first boat came to an abrupt stop and churned up a rooster tail of sand and oyster shells that was every bit of 20' high. The other 2 hot rods had time to throttle down and go into some sort of bewildered holding pattern. If he didn't rip the stern drive out of the transom, it's a miracle.
I had an older fellow that worked for me on the P-3 program that asked me about the effects of sand on water pumps. When I asked him why, he said his FIL and he were boating and hit a few sand bars. He didn't know how it happened, as they were well away from the channel markers. On further questioning, it was revealed that he was of course on the wrong side of the markers. God help him if he ever had to navigate St. Patrick's Creek!