Both sides were missing a swag of key players - many of them on State of Origin duty - at the Kennedy Community Centre on Monday.
The Hawks dominated the middle stages, kicking nine consecutive goals through the second and third quarters of their 16.15 (111) to 14.10 (94) win.
Watson was lively in attack with two goals and some eye-catching marking attempts, while also making his presence felt around the ball.
Josh Ward shone in the absence of injured midfield gun Will Day, with Connor Macdonald, Cam Mackenzie, Dylan Moore and Josh Weddle all busy.
Watson kicked 36 goals last year as the Hawks' premier small forward but can expect more time up the ground in 2026.
"He's had a great summer, he's done everything right and got himself in really good condition, so it wasn't surprising, the way he played," Hawks assistant coach David Hale said.
"We've seen that in the pre-season games and we want to expose him a little bit more around the ball, with Dylan Moore and Connor Macdonald as well.
"Those types of players, we think, can bring a sort of X-factor to the group we've got.
"We think he's going to have a really big year and he's set himself up well."
Calsher Dear was another of the five Hawks with two goals to their names, and recovered from a nasty-looking knee to the ribs from teammate Mabior Chol in a marking contest.
"Calsher likes jumping for the ball, so there's going to be times when he puts himself in precarious positions, but we encourage those guys in front of the ball," Hale said.
"Chol and (Mitch) Lewis had some really good contests today as well."
Hale liked what he saw from former North Melbourne player Flynn Perez, who is in a battle with fellow trialist Jack Riding for the last spot on the Hawks' list.
Perez kicked a superb long-range goal to put the Hawks in front in the second term.
Geelong recruit James Worpel came under plenty of attention from his former teammates and was caught holding the ball by Karl Amon on the wing, bringing the loudest cheer of the day from a healthy crowd.
But he slotted into the Cats' midfield well alongside Ollie Dempsey, who shone in an inside role after making his name on the wing.
"We're trying to add that centre bounce craft to his game and he was pretty dangerous there as well," Geelong assistant James Rahilly said.
Jay Polkinghorne (three goals) put his hand up for a spot in Geelong's forward-line, with injured spearhead Jeremy Cameron and Tyson Stengle in doubt for their season opener.
Shannon Neale (four goals) stood up in attack and Oliver Henry (three) was busy in his first serious hit-out since missing out on last year's finals series after being dropped.
Tanner Bruhn, who was set to play his first game in 12 months, was a late withdrawal because of illness, as was Zach Guthrie.
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