We have been away from Florida for months now and find lots of different kinds of water. There's the open ocean outside the barrier reef. There's the water inside the barrier reef. There's harbor water. There's the kind of water you find in between the mangrove roots. And lately, river water. But you can't drink any of it.
The Dry Tortugas from sea, where there is no water except what they collect from the rain.
To drink it, we have to run it through our desalinator. It uses reverse osmosis, ie lots of pressure, to force water molecules through a porous membrane that stops salt ions. Really really tiny pores. And lots of pressure. And lots of electricity to make that pressure (the salt water is free). We use about 35 watt-hrs to make a gallon of fresh water. Which is pretty good efficiency as such machines go.
The average USA household uses 70 gallons of water per person per day. If we used water at that rate, we would need ten times our solar panel array, which already covers our whole bimini top. Or two hours of generator time per day extra to what we do now (about two hours a week!). So we use a lot less water. In fact we use about 5 gallons per person per day to drink, wash, clean, and do laundry.
Can you cut your (indoor) water use by 35x fold?
Here's how we do it:
Use seawater to flush the toilets (that's about 25% of the typical houshold water use)
Go naked so we don't have any laundry. Just kidding, mostly. We do generate laundry but a lot less than normal and we save up the bulky stuff like bedding for when we are in port with local laundromats.
Shower not more than once a day and use shower heads that a) restrict flow to a fine spray, b) have cut-off valve to stop the water flow when you aren't actually using it on yourself.
Washing dishes with extreme care. This means – turn OFF the water except when it's running on something that needs it – don't run the water until it's hot, just use what you have, it's the tropics and the water is already basically warm - don't fill huge tubs with a gallon of soapy water just then dump that out; instead, get the sponge wet and add soap to it and then scrub a batch of items and then rinse those items – rinse twice using the second rinse on one item to be the first rinse on the next item, and using your hand to sluice the water around on the item not just more water flow - use seawater for washing large items then rinse with fresh – use the minimum soap possible since more soap means more rinsing. Since Jennifer is unable to go to these procedural extremes it seems that I do the dishes a lot.
Let the rain wash the outside of the boat to get the salty crusty stuff off.
What we don't skimp on is drinking it. Turns out that drinking water is the least of our water usage, dish washing is the most.
And the first thing we do when on an overnight ashore is fill up a bath tub with hot water and soak!