Sutton were still 5-4 down after three periods. But goals by Stephen Bayles (2) and Ryan Symington (Photo: Trevor Hyde) turned the tide and Watford were unable to respond until Andy Holt registered his third goal three seconds from the end.
Penguin resisted a late rally by Portobello to complete a 14-11 win while Exeter also won again - 16-8 against Caledonia.