Det Supt Tanya Jones said a member of the public discovered the body in the Basingstoke Canal at Woodham Lock in West Byfleet on Saturday.
Detectives are treating his death as suspicious. Officers are looking into the circumstances that led to him being found in the water.
Police believe they know who the man is and have informed his family, but have not yet released his name.
Officers want to speak to anyone who was on the towpath, lock bridge or nearby footpaths between Friday night and Saturday morning and who might have heard or seen anything suspicious.

Dubbed Scotland's Route 66, NC 500 loops around the north Highlands' coast and interior.
The seven included Commonwealth Games cyclists Lee Craigie and Anne Ewing and British 24-hour mountain bike champion Rickie Cotter.
The time trial over Saturday and Sunday started and finished in Inverness.
The other riders were author and travel blogger Emily Chappell, transcontinental cyclist Gaby Leveridge, plus Zara Muir and Jo Thom, winners of the women's pairs event at this year's Strathpuffer endurance ride near Strathpeffer.
Their time sets a new record for cycling the route.
Scottish endurance cyclist Mark Beaumont previously completed the NC 500 solo in 37 hours 58 minutes.
The NC 500 features several challenging ascents and descents, including the Bealach-na-Ba at Applecross.
The unclassified road rises to about 626m (2,053ft) over about four miles (8km).

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Caley Thistle need to beat Well to stand a chance of Premiership survival.
Victory, coupled with Hamilton Academical dropping points to Dundee, would see Inverness avoid finishing bottom, and automatic relegation, at the expense of a two-legged play-off.
"The players need to look after themselves the next couple of days," Foran said.
"We must go into details: what are you eating, what are you drinking? Don't get off your sofa, find babysitters for your kids - it's worth it, it's worth it. We need you to give your all now.
"It's a massive game, but it's one you go and enjoy, one you take to Motherwell, whereas the Hamilton dressing room before their game will be very, very nervous."
Inverness remain one point behind Accies at the foot of the table, heading into the final round of league fixtures.
Their outlook seemed bleak when they were thumped by rivals Ross County in the first of the post-split matches, leaving Caley Thistle five points adrift.
But wins over Accies, then Dundee on Wednesday night, have kept alive the Highlanders' hopes of retaining their Premiership status.
"It was a wonderful, wonderful performance (against Dundee) and we need it again on Saturday against a top team," Foran added.
"Motherwell have got two really good strikers, a strong midfield, defensively we'll have to be right at it once again.
"All the pressure that was on our shoulders goes straight to Hamilton. We can't influence what happens at Hamilton but I do know, I've been in football a long time, they'll be feeling a hell of a lot of pressure right now.
"There's no sugar-coating it, no hiding it, that pressure's lifted off our shoulders and goes straight onto the Hamilton players. It's a huge game for them, and we need the same passion, hunger, desire, as we had last night, and what will be will be."
Foran insists he has no interest in keeping tabs on Accies' progress at New Douglas Park, as his side do battle with the Steelmen in Inverness.
The former Caley Thistle stalwart, who made over 150 appearances for the club, has painful memories of their last top-flight exit, when a 1-0 defeat by Falkirk in 2009 sealed their relegation.
"I missed a few great chances, so that haunts me to this day," Foran said. "We gave 100% effort and that's all you ask from the players now, 100% effort and commitment for the jersey.
"The supporters were magnificent last night, I'm sure they'll be down in their droves again. We're going well, we're full of confidence and we can't wait for it now."
A man's body has been pulled from a canal in Surrey.
[NEXT_CONCEPT]
Seven women cyclists have set a time of 36 hours to complete the gruelling 518-mile (833km) North Coast 500 in a non-stop team time trial.
[NEXT_CONCEPT]
Inverness boss Richie Foran has urged his players to rest ahead of Saturday's seismic clash with Motherwell.