Chilmark and Aquinnah police rescued four swimmers from a large rock off the North Shore in Chilmark late Friday, two of them in distress.

The call came at 6:45 p.m. Friday that a father and son were swimming off Great Rock Bight Preserve, a land bank property off North Road in Chilmark. Conditions were rough with an onshore wind and three to five-foot waves. Police said the father became distressed and the son swam out to help and became distressed himself. Two people on the beach saw what was going on and swam out to help. All four people wound up clinging to a large rock, trapped in the rough conditions, police said.

Chilmark police arrived on the scene and an officer swam out with a life jacket for the father.

Aquinnah police responded in the Wampanoag tribe’s natural resources department boat. The father and son, who were not identified but described as ages 40 and 14 and from Connecticut, were transported to Menemsha harbor for waiting EMS.

The father was transported to the Martha’s Vineyard Hospital where he was treated and released.

Coast Guard station Menemsha and Massachusetts Environmental Police also assisted.

The Coast Guard put out a press release about the incident early Saturday. Chilmark police provided more details in a release sent out Sunday.