Sara Markwith and Rachel Godfred, both 17-year-old co-captains of the Mercer Island High School varsity swim team, put their endurance to the test today when they attempted to swim all the way around their hometown — a distance of 14.6 miles.

For some, finishing high school requirements means sweating algebra two. For a pair of Mercer Island teens, it meant swimming around Mercer Island aided only by wetsuits and flippers.

Sara Markwith and Rachel Godfred, both 17-year-old co-captains of the Mercer Island High School varsity swim team, put their endurance to the test today when they swam all the way around their hometown — a distance of 14.6 miles, according to the Mercer Island Parks and Recreation Department.

The girls left the shore at 6:15 a.m. and finished about 12:45 p.m.

Students at Mercer Island High School must complete a “culminating project” of their own creation in order to graduate, the girls said. Markwith and Godfred chose to tackle the Island’s circumference. They solicited friends and family and raised about $3,000 for Seattle Children’s Hospital with their athletic feat.