MOWSA currently offers several solo, sanctioned swims that challenge marathon swimmers over long distances in cold water.


Boston Light Double (BLSx2) – 16 miles (25.8 km)
M Street Beach, South Boston to Little BREWStER Island and Back to M Street Beach, South BOston

The Boston Light Swim, the “Granddaddy of American Open-Water Swims” and the Boston Light Double have a ton of history.

The BLSX2 is a tide-assisted, cold water swim. It starts from M Street Beach in South Boston, winds though the Boston Harbor Islands (which is a national park) out to Boston Light on Little Brewster Island. The Double is completed when the swimmer returns on a flood tide along the same course, back to the M Street Beach.

What to expect

Water Temperature: 58 to 68 degrees F

Tides: This swim has to be tailored to the swimmer's pace. You start at the M Street Beach in South Boston with the ebb tide and need to reach Boston Light on Little Brewster Island within 30 minutes of slack and swim back to South Boston on the flood tide.

Weather: Anticipate ocean swells, wind, waves, and overcast skies. You may get glassy water or four-foot swells. This is New England; expect it all.

Swimmer notes: The swim starts from a sandy beach. Little Brewster has a pebble/rock beach. The finish is back at the sandy M Street Beach. The water temperature is coldest at Little Brewster Island. The swimmer is allowed time to reapply sunscreen and anti-chafing products before starting the return swim, but you should not linger too long--officially you have just 10 minutes to begin the return trip or the swim is terminated. Plus, standing around wet after exiting 58-degree water can quickly lead to hypothermia for most people. You'll be in the open ocean for the duration of the swim, so expect to encounter some marine life.

Solo Records

Crossing Number Name Nationality Date Time Notes Observer
1 Samuel Richards USA August 13, 1913 13-plus hours First, Charlestown Bridge to Lighthouse and Back (24 miles) Historic
2 Charlotte Arne USA September 3, 1934 13:36 First Female Historic
3 James Doty USA September 22, 1969 9:30:00 First, M Street Beach to Lighthouse and Back (16 miles) Historic
4 Elaine Howley USA August 12, 2010 7:07:10 Fastest Female, First Female on 16-mile Course Fred Knight
5 Greg O'Connor USA August 12, 2010 7:07:10 Fastest Male Fred Knight
6 Helen Lin USA August 7, 2015 7:56:26 Elaine Howley
7 Tommy Gainer USA October 7, 2016 7:23:49 Greg O'Connor

Banner photo by David Boeri