In the noon heat you rinse the deck with a bucket of water; the salt vanishes, the wood darkens for a moment, then opens again under the sun. Stepping out of the shower it is not that faint dryness on your skin but the softness fresh water leaves. No one thinks about it. The tap opens, water comes; warm, clear, without salt. And yet all that blue around you cannot be drunk. Fresh water aboard comes not from the sky or the shore but, most often, from a machine beneath your feet.
The machine is called a watermaker. And how it works is simpler than it looks.
How Seawater Becomes Drinkable
A watermaker pushes seawater through a very fine membrane at high pressure. The pores of the membrane are so small that the water molecule passes and the salt cannot; fresh water gathers on one side, while seawater with its salt concentrated returns to the sea on the other. This is called reverse osmosis. The science is not new, but shrinking it small enough to fit a boat is relatively so. Depending on its size, a watermaker can produce up to a few hundred liters of fresh water an hour — enough to meet a mid-sized gulet's daily need without ever tying up ashore. It is usually run while the engine or generator is going, since making that pressure takes energy. The skipper often runs it in the afternoon, once the tank is half down; by evening the tank is full again.
Managing the Water
However good the machine, water at sea is always something managed. Experienced crew do it without lecturing: the washing-up is not done under a running tap but rinsed first in a basin; seawater is used for the deck wash, the fresh kept for drinking and bathing. The membrane itself asks for care — left unused a long while it must be preserved, and cleaned regularly of salt and sediment; a neglected membrane both lowers water quality and, when it must be replaced, burns the pocket. So on a well-run boat the watermaker is overhauled at the start of summer, measured through the season, and preserved toward winter. The guest sees none of this. They only open the tap, and water comes.
There is a side of freedom to it as well. A boat with a watermaker need not turn back to a port or a jetty every few days to fill a tank; it can stay longer in far coves, away from the crowd. Which is to say the machine is not only comfort but range. If you can stay three days in the quietest cove, you owe some of it to that pump running softly beneath your feet. Independence at sea is often measured in small, unseen systems like this.
After the evening shower, come up on deck. Your hair still wet, the air gone cool, the tank full again. For miles around you there is water that cannot be drunk; but yours, just as much as needed, is fresh.
YACHT MANAGEMENT →