(CBC)(CBC) A woman disappeared in rough waters in Lake Erie off Pelee Island on Monday afternoon while trying to rescue a struggling swimmer.

The woman, who is from Calgary, and another woman took a raft out to the swimmer after they noticed he was in trouble, Essex County provincial police said.

During the rescue, one of the women disappeared in the water. The Ontario Provincial Police marine unit along with the Canadian Coast Guard and several private vessels are searching for a missing woman in Lake Erie off Pelee Island.The Ontario Provincial Police marine unit along with the Canadian Coast Guard and several private vessels are searching for a missing woman in Lake Erie off Pelee Island. (Submitted by Heather Greene)

The man, from Bright, Ont., was unharmed, police said. Police said the man and the two women are related, but they didn't know more about their relationship or why they were on Pelee Island.

The provincial police marine unit is searching for the woman along with the Canadian Coast Guard and several private vessels, one of them belonging to an off-duty coast guard captain.

No names have been disclosed.

The incident occurred near East Shore Road, on the east side of the island, which is southeast of Windsor.