The striker enjoyed another good performance after impressing against Crystal Palace in midweek.
The youngster was once again named as a substitute for the Black Cats, having featured on the bench against Crystal Palace on Monday as well.
As in that game, he came on to make a telling impact, with this fixture seeing him bag his side's second late on to secure three vital points.
It was a proud moment for him as he bagged his first goal at the Stadium of Light, and Watmore is hoping it will help his side to build some momentum going forward.
“It’s a massive win for us today and we know that. To score in front of those fans was a special moment for me,” he told safc.com.
“It’s such a hard league, when you’re winning away from home and then at home, you’re taking that into your next game and that can only be good.”
“We knew we needed two wins and that’s what we got. Hopefully we can take this momentum into our next few games and go from there.”
The win was certainly a big one for Sam Allardyce’s side, as it moved them out of the relegation zone at the expense of fierce rivals Newcastle United.
The Black Cats now sit 17th in the table, and two points clear of Bournemouth and the Magpies in 18th and 19th respectively.
They are, though, starting to show good form, having won as many league games in six games under Sam Allardyce as they had in 17 under Dick Advocaat.