The colregs clearly say the vessel need not be diplacement. In that
sense, a ski is simply overloaded and sinks when not planing. They also
float without people on them!

Cheers MC

Simple Simon wrote:

You are clearly wrong. A kite board sinks when the
operator stands on it. A water ski also sinks when
the operator stands on it. Clearly neither is a vessel.

A barge floats when cargo or people are on it. Even if
it has no power it can drift from place to place with
the winds and current. A barge clearly is a vessel.