Water Move for Spaceships

[Christopher R. Rice]

I'm attempting to work out a proper method for giving a spaceship design (from GURPS Spaceships by the most excellent Mr. Pulver) a water-based movement. Other than the maddeningly unhelpful line from the Star Galleon, there seems to be no easy way to do it.

Originally Posted by Spaceships 7

A star galleon is a wooden-hulled sailing ship, but it is
equipped with enchanted astral sails enabling it to fly in the air
and voyage through space. It uses a 300-ton (SM +7) streamlined
hull 90 feet long with nautical lines. It also functions as a
conventional sailing ship.

There seems to be the hint of having regular sailing vessels with the capacity to move through water...but no actual rules for it. I know I could just rule it to perform as a vessel of a similar nature but I'd rather have some sort of solid guidelines I could use. I've got a few odds and ends I've toyed with but I'll be honest, they seem sloppy and contrived to me. So I've come to pick the ginormous collective brain of the fora. :)

So thanks much for anyone who replies!

Ghostdancer