It is probably best to start explaining the terms to them by referring to the origin of the word. If not they may think that the reason the word Heads is used for a marine toilet is because the space is so small and cramp that with the yacht rocking you regularly hit your head. That is true, but not the real reason for the name HEADS
In the older days the square riggers had limited technology and space. The "out-house" was situated on the side of the bow of the boat. Since they used the term of head for the bow of the boat, it became common to say:"I am going to the Heads"
The reason for putting the heads on the side of the boat was very simple:
- Square rigs sail down wind, so putting the heads at the bow, would let the foul smell be blown off the ship instead of into the Captains beard
- At the bow the ship is narrower that the stern, so all human waste would fall directly into the water and no need for appointing a janitor
Next time you have a few novices onboard, tell then the story before you say:"I'm off to the heads"