single word requests - An adjective to describe "being at sea"

I'm looking for an adjective that describes the fact that a ship is sailing at sea. Much as "afoot" describes a person being in the state of walking. I was hoping "asail" would be a word, but can't find it from Google.

The word would replace the square brackets in the following example:

In Plato's ship of state metaphor, a ship is [sailing at sea], helmed by a captain ...

Answer

You are looking for afloat:

1. floating


2. out at sea