Kurz has an interesting concept, which might be even better than the cabin cooler. If I understand correctly, he is suggesting sprayed roof cooling for a boat. This would address the daytime solar radiant heat load effectively. Of course, spraying seawater over your decks might bring a few issues, but it's a cool idea. Basically, stop the heat from getting into the boat in the first place... and provide radiant interior cooling through the cooler outside surfaces. Neat idea that might be easier to try than to analyze.
I can't find any performance data for the cabin cooler. The only video I found on YouTube was not very informative - not even a single temperature measurement.
I've done chilled water cooling design on numerous buildings, and find the basic concept of the unit to be sound. There are conditions, and equipment selections which could work well using this concept. Performance will be determined by the ambient conditions, desired cabin temperature, water temperature, fan air flow rate, coil characteristics, water flow rate, and in this case, the under water heat exchanger.
In the south US, we typically use a chilled water temp of 45 deg F - primarily to create an indoor dew point condition around 55-60 deg F. We are looking to dehumidify significantly while cooling to produce comfort. If your ambient dew point is already about 55-60 deg F, dehumidification is not really essential, so you could get away with warmer water. Looks like the water temp at Vancouver is around 53-54 deg F in July. If you were using direct sea water, you could expect a leaving air temp in the 65 deg range without getting a really deep coil with a lot of heat transfer surface. At an air approach temp of 10 deg F, you could probably maintain a cabin temp around 75 deg F in a dry climate with a good coil and 150-200 cfm air flow (wag numbers), as long as ambient conditions weren't too harsh.
The cabin cooler appears to use a closed loop concept with an underwater heat exchanger. So, we have two separate heat exchanges for the water and two approach temperatures to deal with. You can't move heat without a temperature difference. So to push heat from the cooler heat exchanger to the loop water, there will be an approach temperature, and from the loop water to sea water there will be another. Now, our 65 deg F leaving air is looking more like 70-75 (in the absence of actual performance data). Plus, I've got a closed loop system to fill and air-bleed to get working properly; and re-bleed until the majority of dissolved air is removed from the water loop. We can still cool the cabin with these air temps if we have a large enough fan and coil for the conditions.
The way the video shows the unit being used, is blowing directly on the occupant who is lying in front of the air discharge. If the cabin is 90-95, or even 85, and you're lying in a 75 deg air stream, it's an improvement. If you expect to cool your entire cabin down to 75 deg, you probably need to ask for performance data before buying. The only price I saw referenced on the net was around $450. For that money, I'd want more to go on than just pictures of the equipment. That's getting up in the range of equipment with rated performance data - granted modifications will be necessary to adapt for 12volt use.
Now, if you can get cooler water, say 45 deg F, you get into a situation where the unit is likely to produce condensate. So, you're lying in bed with something that's wetting the sheets like weird Uncle Joe after a hard night drinking.
Being from the Deep South where our water temp is well into the 80's now, I have to wonder if night cooling is a necessity when you're sitting in a large body of 54 deg F water. I get it for daytime, when the temp might spike up due to solar radiation, but in the dark, everything below the waterline, including the ballast tank will be approaching 54 deg in a reasonably short time - producing significant radiant cabin cooling. I guess I'm wondering if this unit is really necessary, for other than mid-day naps, in the regions where it will actually work.
https://m.youtube.com/watch?v=vKs9h_-7sVo
