Exeter went from 4-1 down to lead 7-4 in the second period only for Watford to hit back and take an 11-8 advantage after three. Watford looked to have secured the points when goals by Andy Holt and Corcoran made it 13-11 with only 1.32 to go.
Even then, there was time for Exeter to level at 13-13 thanks to two goals by Kameron Powell. Then, in a final attack, Watford fired against the woodwork, only for Corcoran to push the rebound over the line. Watford will have been grateful to goalkeeper Karan Basu for some fine saves - notably, a superb penalty stop earlier in the match.
Later, Watford were involved in another dramatic match against Penguin, which ended in a 12-12 draw. Josh Barrett was the Watford hero, having the strength late in the final minute to turn his defender and earn a penalty - which he then converted for a final equaliser.
At East Manchester, Sheffield completed two wins in Championship 1 - 16-12 against Caledonia, then 14-6 against Lancaster.
In men's Championship 2, Worthing enjoyed two emphatic victories at Haberdashers - against Southampton (18-8) and Otter (17-4). Sedgefield also won twice at East Manchester, stealing a late 12-11 victory over Manchester Hawks, then beating Invicta 17-10.
Photo (Trevor Hyde): Zac Corcoran lines up a shot against Exeter keeper Toby Hogg.