It’s not equivalent to a noun phrase with an adjective, but to a copular sentence.

In other words:

Beau le bateau, dansant sur les vagues (Beautiful the boat, dancing on the waves)

= Beau est le bateau, dansant sur les vagues (Beautiful is the boat dancing on the waves)

= Le bateau dansant sur les vagues est beau (the boat dancing on the waves is beautiful)

This is an example of archaic syntax, mostly used in poetry, although it can be used in speech, with a slightly different prosodic pattern, when giving an opinion about something:

Pas mal, ce bateau (Quite nice, that boat)