WATCH: Rob Gronkowski and girlfriend Camille Kostek battle it out for $20,000 in charity

Four-time Super Bowl champion Rob Gronkowski and his girlfriend Camille Kostek competed on Good Morning America in a cold plunge challenge for charity on Friday morning.

The two were immersed in 44-degree cold plunge tubs in the middle of New York's Times Square on the chilly, gray morning. Whoever stayed in the plunge the longest won $20,000 for their respective charities. Kostek was competing for The Peter Frates Family ALS Foundation while Gronk competed for his Gronk Nation Youth Foundation.

Former New York Giants defensive end and GMA co-host Michael Strahan hosted the competition. Strahan told Gronkowski that the cold plunge would be great preparation if he was considering an NFL comeback. The former NFL tight end joked he would only do so if Strahan did.

The challenge was to stay in the frigid water for four minutes. With less than 30 seconds left, Rob Gronkowski hopped out of his cold plunge tub. That left Kostek as the winner of $20,000 for her charity. Gronk was awarded $5,000 for his youth foundation.

Camille Kostek said competition brought her and Rob Gronkowski together

Michael Strahan asked Camille Kostek if she ever thought she and longtime beau Rob Gronkowski would compete in a cold plunge. The Sports Illustrated model said she wasn't surprised, noting that competition was something that the two bonded over when they first began dating.

Kostek said:

"I'm not really shocked by this. I think what brought Gronk and I together was our love of competition."

The couple also co-founded their own digital sweepstakes platform. It's a way to reward those who give back to their local communities. The non-profit offers different campaigns that people can enter by proving how they contributed. The prizes include luxury items, including high-end vehicles.

Gronk and Kostek first met at a Thanksgiving event in 2013 when the tight end played for the New England Patriots and Kostek was a cheerleader for the team.

It was frowned upon for players and cheerleaders to date, but that didn't stop Gronk from sneaking his phone number to the then-Patriots cheerleader with the help of another teammate.

The two didn't make their relationship public until 2015, and they have been together ever since.