Despite having his shirt undone with bare feet, Paul still seemed to be wearing smart trousers and a shirt.
The 70-year-old protected his face from the sun wearing a turquoise baseball cap, with his hair poking out beneath it.
His wife, Nancy, was far more suitably dressed for the warm weather in a pretty dress.
The floral number fell to the middle of her thighs, displaying her shapely and slim legs beneath.
She teamed the flattering dress with a white fedora hat and she carried a large beach bag with her.
The elegant New Yorker accessorised her outfit with a minimal gold chain and a couple of bracelets.
The evening marked their second New Year together as husband and wife but rather than planning something big to see it in, they seemed happy to do something more relaxed.
Nancy, 52, gazed lovingly at her husband as they made their way on the boat, while Paul seemed very relaxed and content.
The holiday in the St Barts marked the end of a busy year for Paul.
Earlier this month he joined the remaining members of Nirvana on stage at the Sandy Concert at Madison Square Garden, stepping into the shoes of the late Kurt Cobian.
At the time Cobain's widow Courtney Love admitted she was 'not amused' by him standing in, revealing she would have been happier for John Lennon to strand in for him.
Nancy and Paul recently enjoyed the wedding of their close friends Ronnie Wood and Sally Humphreys.