While much of the nation may have started the new year with a sore head, others marched and swam their way into 2018.
The streets of central London gave way to more than 8,000 performers for the New Year's Day parade.
American marching bands joined acrobats and dancers from all over the world for the annual celebrations.
Elsewhere, thousands of swimmers braved the icy waters of Britain's shores at events across the UK.
Now in its 32nd year, the New Year's Day parade attracted thousands of spectators along its route from Piccadilly to Whitehall, and was broadcast to millions more around the world.
Themed "showtime", it featured horses, giant balloons, vintage cars and cheerleaders, including entries - a float or performance - from individual London boroughs.
Ski jumper Eddie Edwards - Eddie The Eagle - was a recognisable face among the performers.
There were more costumes to be seen in other parts of the UK, but some of these ones got a soaking.
In Pembrokeshire, more than 1,500 swimmers braved the sea - many in fancy dress.
A mass dance warm-up took place at Saundersfoot before the swimmers took the plunge, cheered on by thousands of spectators at the annual event.
There were similar scenes in Scotland, where more than 1,000 people got in the Firth of Forth for the New Year's Day Loony Dook.
The sell-out event began with a parade along South Queensferry's High Street before the hardy participants went for a dip.
Meanwhile in Derbyshire, an unofficial tradition saw some people jump off the Okeover bridge into the River Dove in Mapleton.