I'm building a house on a 40 acre lake. There are other houses around the lake with a few boats occasionally. My part of the lake is shallow - about 4 feet. I'm building a boathouse soon and was wondering how well it would work to dig out the part of the lake that's under my boathouse (10'?) so I can install a geothermal system in my new house. I'd like to put it under the boathouse to protect the pipes from boats, fishermen, anchors, etc... My concern is that the dug out area eventually would get filled back in with dirt. I've considered putting in an underwater retaining wall to keep the dirt out. I suspect that would work for some time but might restrict water flow which I understand is important for cooling the pipes. I live in Texas, so air conditioning is far more important to me than heat. Will this work?