Both teams hold their practices during the summer, and he said he realized he would have to give up one activity.
Clark has stuck with music - he was a tuba player for Boyle's band, which one a state championship this season. But because high school swim teams practice in the late fall and winter, he was able to get back in the water as well.
"My friends mentioned that I should do it, and I kind of missed it, so I decided to start up again," Clark said.
Clark is used to winning as part of the Boyle band - the band won its third consecutive state championship this fall. And he has already won several races at Boyle's swim meets this season.
"I'm just looking for the most success I can have," he said.
He said he's glad to be part of a successful team, one that is expected to again contend for a regional title after finishing second last season.
"I think we've got a pretty good shot to win the region," he said.
Clark said one of the things that appeals to him about swimming is that his success depends solely on what he does.
"I missed my performance deciding how well I did," he said. "In band everyone has to work together at the same time to achieve the goal. Here it's all on me."
Clark said the practices for marching band and swimming are equally demanding though they're decidedly different.
"It's mental in band and it's physical in swimming," he said. "The competitions are two different worlds."
Clark said he isn't as sore as he was after the earliest swimming practices, when he was using muscles that hadn't been so active in years.
"I could definitely tell it had been a long time," he said.
"I expected to come back and pick up where I left off. It was definitely a challenge. But things are turning around now."