The Coast Guard was combing the waters off Florida’s Gulf Coast early Wednesday in a desperate search for a missing sailboat carrying a father and his three teenage children who were “attempting to survive” in rough seas, and who had not been heard from since Sunday.

 The U.S. Coast Guard launched a  HC-130 Hercules airplane from Clearwater, and several other vessels from Stations Cortez and Fort Myers, Petty Officer 2nd Class Ashley J. Johnson told the News-Press. The Maritime Emergency Response Team had also been activated.

The family, which the Coast Guard said lived on the 29-foot boat, was last heard from Sunday when the father called his his brother. They were being buffeted by six-foot waves off the shore of Englewood and were “attempting to survive,” the Coast Guard said in a statement.

A concerned relative called the Coast Guard on Tuesday.

Englewood is north of Fort Myers in southwest Florida.

The man, his sons, ages 13 and 15, and his 17-year-old daughter left Sarasota at 7 a.m. Sunday, the Coast Guard said. The quartet was heading for Fort Myers to have repairs done on the sailboat.

The boat reportedly had no name and no radio, according to CBS.

Mariners with any information were asked to contact the Coast Guard’s St. Petersburg sector at 727-824-7506.

The Associated Press contributed to this report.

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