Pentagon's Hongseok showed off his outstanding swimming skills on the December 28 episode of MBC's 'Real Men'.

During the episode, the contestants began to train in combat swimming, starting with a special swimming exam, where Hongseok went up against Jeon So Mi's father Matthew Douma. Ahead of the exam, he shared that he was confident he would beat his opponent and be accepted into the advanced swimming class.

"When I was studying abroad in Singapore, I was the top athlete swimmer in my school," he remarked.

As it turned out, Hongseok ended up being the only one who made it into the advanced swimming class, not only beating Matthew Douma, but showing impressive skills in treading water and being able to swim across a 1.6 kilometer (approximately 1 mile) distance.

Watch Hongseok's skills in action above!