This Alberta dad sat through 30 hours of tattoo pain so his son would feel better about birthmark

Eight-year-old Derek Prue was playing with his sisters in a hotel swimming pool earlier this month, when his dad called out to him from the pool's edge.

Derek looked at his father and fell back into the water, his eyes wide and a huge smile on his face. His dad, Derek Prue Sr., unveiled a new tattoo, a replica of the birthmark that covers a large part of Derek's torso.

"I was happy and I was a little confused," Derek told CBC's Edmonton AM. "I didn't know he was going to do that."

Prue said he decided to get the tattoo after noticing his son insisted on wearing a shirt when they went to the pool.

WATCH | Derek Prue gets tattoo to match his son's birthmark:

"I knew he was self-conscious about it," Prue said, choking up. "I saw how he was reacting, and it made me want to do it so that he wouldn't be the only one."

Derek says he was a little suspicious when his mom asked to take pictures of his birthmark, but he didn't know what his dad had planned.

'It's pretty painful'

Apparently Prue didn't know what he was in for either.

"He's been through the wringer sitting for that," said tattoo artist Tony Gibbert, owner of the Juicy Quill tattoo studio in Stony Plain, Alta., where Prue had the work done. "It's pretty painful."

Prue recalls his first session: "I remember the first time coming in, laying down and then after maybe three, four hours, I was like, 'Yeah, are we almost done?' And and Tony's like, 'Yeah, we're almost done the outline.'

"I'm kind of glad I didn't know how long it was going to take."

Gibbert says he was happy to be a part of the project which took about 30 hours over six to eight weeks to complete.

"I think it's amazing to be able to comfort your son like that," he said. "It's more than just your kid seeing your name, or something, you get to actually, like, really change the way he feels about himself.

"Just being able to go swimming with his dad and take off his shirt and be happy and comfortable. I'm happy I get to be part of it, in a small way I get to help with what he's trying to do."

When Derek's mom Shanel Prue asked him if he'll go swimming without his shirt after the pool reveal he said he would.

"Whenever Daddy's there I can take the shirt off."

For Prue, it's all worth it.

"Now we have the same marks for life."