I was involved in building an AC unit for a houseboat that worked off the lake. I did many tests to determine the optimum depth to pick up cold water, what the temperature was there, how much cold was lost on the way up the hose and etc.... I owned the boat with a friend who was an engineer. Before we ever got around to building it, I got interested in another houseboat and sold out my share.
However, my friend continued to work on the idea and ended up building the unit. I think he did a really good job of following the orginal idea except he didn't use the optimum radiator setup (in my view) to get the most cold out of the water. Of course in proper physics terms I should say, "in order to put the most heat into the water".
However, here is how it worked. He used an RV water pump connected to a largish garden hose, Craftsman real rubber hose. It was sunk 50' in the lake (Cumberland is a deep lake). The end of the hose had a filter screen on it (large fish basket) to keep leaves and other lake monsters from getting into hose. The reason this works, is technically from a pressure point of view, the pump is only pulling water up from the lakes surface to the pump, a mere foot maybe. The water was pumped through an AC condenser, a 12v auto fan blew through that. The excess was dumped overboard. Incidentally the condenser accumulated condensation. So, this had to be housed in an aluminum box he made with a low point containing a small bilge pump to pump out the condensate as it accumulated.
The unit was capable of pulling the inside of the houseboat down about 10 degrees. Made it nice inside when you'd walk out of 90 degree humid into 80 degree dry air.
In retrospect, the unit would have been even better using a type of condenser with wider gaps in the fins and larger copper tubing. I had wanted to use a large transmission cooler for the heat exchanger. In fact, I wanted to use 2 of then, both fed at the same time with a manifold. This way, the hot air saw the first cool condenser, cooled off x-degrees, then pass through a second cold exchanger and drop x-more degrees. Maybe 3 would have been even better to get every last degree you could out of the air and into the water. It's important to know that from 50 foot of depth, you get water that is in the range of 54-56 degrees coming into the boat. So, I think with the right setup, you could possibly get 60 degree air out of the heat exchanger array. As well as it worked, it could have worked much better. Also, the unit should have been built above water level if possible so the condensation could drain out without any energy. The fans could have been a squirrel cage for more efficiency (sorry, no computer fans, you need some real head pressure to force air through condenser fins). And, a simple bilge pump could have been used to flow a lot of water at low pressure. The antique belt drive RV water pump he used had a big motor, belt drive, it was a 12 volt high pressure monster. Both the overdone fan and water pump cause him to have to run idle a 1000 watt generator just to hold the batteries up. Little more thoughtfully laid out (in other words, buying the right parts rather than using the sub optimal free parts) would have made it even more successful. Probably not more than an extra $200. Still, it worked very good as it was.
Now, you might ask, how do you use a bilge pump to get water up from 50 feet below the boat? It's simple and I tested it. I took a bucket, connected our nice rubber hose to the bottom of the bucket. You weight the bucket so it sits with the bottom about 14 inches or so below the water. As far as you can without sinking it. The cold water from below shoots up in a nice pillar filling the bucket. As You put the bilge pump in the bottom of the bucket pumping into the heat exchange array. The outlet of the heat exchanger array is put over the side of the boat down below the level of the lake. Now the head pressure the pump is working against is only the difference in the level of the buckets water surface to the actual lake surface. Maybe a few inches. And, the pump is always below water so there is never a priming issue. You can move LOADS of water for very little current in this way. We're using mother nature, (gravity) to fill the bucket and the pump to move it only from the bucket.
I know your not setup next to a lake, so this idea can't work for you unless you can find some shallow water table nearby, pick the water up in volume form one hole and return it to another some distance away. Just some more ideas to throw out there. The advantage of a setup like this in your camper, is your not in danger of a leak sinking it.
Things are always more complex on a boat, pesky sinking.....