. However, in general, the oceans have gotten dirtier & busier with many more cruising boats crowding anchorages over the years, many if not most dumping their raw sewage right there where anchored where we would be washing dishes & brushing our teeth.
Yes, and indeed these are not places where you should be using a water maker.
The water tank you have in your 2003 C Dory is on the port side. There is still room for another tank/bladder tank under the V Berth. Also the direct conversion (after appropriate sterilization) of the aft holding tank, since it is not being used, is a viable option..We do have a 2003 C-Dory & the water tank is already in the bow under the V Berth, so no putting any other tank up there. We have considered putting in a water bladder in the back in the holding tank that we are not using as we have a composting head, but that project would be difficult to get to & figure out
I Cruised Baja from the mid 1960's until 1996--I am sure that there are more boats there now than were in the past. But I suspect that you can still find plenty of areas where there are not other boats polluting the water.--if necessary pick up that 5 gallons of sea water you might need in a non polluted area.
specific advice from any Cbrat that has installed a 6 to 8 gallon an hour watermaker that draws less than 15 amps.
I doubt that you will find anyone who has a water maker which only draws 15 amps and puts out 6 to 8 gallons an hour. in a compact space. The closest you will find is the Village Marine (Parker) "Little Wonder" 12 volts, 15 amps, 6 gph... (The Rainman 12 volt unit uses 32 amps...to give that type of output). Then there is the "neat and compact" part. Where are you going to put these components? Where have you put the refer and freezer? What other storage space will you give up (I assume that you probably already ditched the water heater.). You have 370 Watts of solar panels: are you going LiFeP04 batteries to save weight and space to fully utilize that amount of solar energy?
I don't know if you have queried the cruising forums--but I would check out the section on water makers. There are a number of queries there, and a lot more depth of knowledge than among the C Dory owners.