Just bought a new house and want to install geothermal. Local HVAC quotes 47K. Hahahahah! I installed my last system for 13k. So, we back to a flood plain and the headwaters of a tidal river. My neighbor 300 feet down river has a pier. I think I could run pipe off my back yard and into the flood plain(county owned), into the tidal mud and then into the "deep" water (maybe 5') I'm scratching my head. Such a resource so close. How to utilize it? We could just drill wells, but that is not really a challenge I've never seen any loop that will function in such an environment. There is always the danger of boats heading into the shallows and the props hitting stuff underwater. Has anyone ever set up a custom engineered loop in an environment anything like this? If some kind of standard heat exchanger (300' rolls of pipe,slim jim,etc) won't work, what about pumping river water out of the river and passing it thru a custom made, no clog HE (heat exchanger)? Then run the loop water off the HE? I suppose I could try and pipe out to the deeper water, but that is a really long way. 1500' feet total. At least 1000' down a public waterway I'm in Maryland and this is a Chesapeake bay feeder. I don't know the year round water temps. Any ideas?

Putting your expensive slim jim in a tank on shore instead of where it can be hit by boats makes sense if you can't get deep enough. If you can only use shallow water that goes away at low tide, then you need to use a larger heat pump and store the hot/cold in a tank (preferably in the house).

generally speaking installing a loop field on public property opens you up to fines/tickets/disaster (damaged loops in the winter because of some project).
That said it is not unheard of even around here I've knowledge of folks with loops under state land.
Since flood plan offers lots of damp soil that is a great place for horizontal loops.
j

You could do raw water with a indirect heat exchanger and as long as you can keep organic and biologic material out of the intake. It would be the least problimatic, i.e. if a single line got cut it would be easily replaced. The other option would be to drill a shallow sump well that would draw the river water in through the alluvial sands to act as a natural filter.

Years ago a local company was harvesting salt water from the bay for their product. The intake continually was clogged with flounder and or horshoe crabs. What I described above solved the problem.
Eric