Usually, the last thing you wanna see while stranded in the water is a shark … but this time, it was a GOOD thing — ’cause “Shark Tank” star Robert Herjavec saved the day by rescuing an ex-hockey player and his family during a boat trip on the lake!!

Here’s the deal … 41-year-old Tom Lawson — who played 10 years in several different leagues — was out with his wife and kids on Lake Joseph in Ontario, Canada … when their boat ran out of gas.

To make matters worse, the sun was going down and Lawson’s boat was not meant to be out at night … so the whole family started flailing their arms and calling for help.

As it turns out, the businessman was out on his jet ski at the same time … and noticed the family trying to get his attention.

My granddaughter posted this of the superhero shark @robertherjavec who towed them to safety today on lake joseph.

“My first thought was they must love ‘Shark Tank,’ but then I realized they were out of gas and stranded,” Herjavec told People.

The Shark says he immediately sprang into action and found a rope to tie to Lawson’s boat … and towed them back to land with his jet ski!!!

Thank you @robertherjavec for rescuing my daughters family stranded on Lake Joseph Canada today ?? nice tow to help them back.

The group was extremely thankful for the rescue … and even posed for a pic with their hero.

Awesome stuff … but we’re sure Tom will be sure to fill that tank up next time!!