A 20-year-old Anne Arundel County man drowned last week in the Chesapeake Bay after leaving a pier to retrieve a girl’s hat, authorities said.

The man, Thomas Brown of Churchton, who was widely known and liked in the area, left a nearby pier on July 22 to go into the water after the hat, according to authorities and the accounts of friends and acquaintances.

But Brown did not know how to swim, the Maryland Natural Resources Police said, and he vanished in the water.

Brown was going to be a senior at Southern High School in Harwood, where he was enrolled in a life-skills class for students with mild to moderate disabilities, said the school principal, Marc Procaccini.

He was a “very, very positive young man” with a contagiously upbeat attitude, Procaccini said. He touched the lives of many people at school and in the Churchton community, the principal said. “I think everybody in that community knew him.”

Brown was “always visible riding his bike, or down at the pier fishing, or walking down the street listening to his music,” the principal said, adding that Brown “was a really good kid.”

A search was carried out until dark on the 22nd, and Brown’s body was found Tuesday near the Franklin Manor community pier, the Natural Resources Police said.

An effort to help his family was set up on Facebook.

On the Facebook page, a woman called Brown “a truly special person.”

She said she “was lucky enough to be his teacher for 6 years.”

Last month, Maryland Gov. Martin O’Malley (D) joined the Natural Resources Police in urging anyone planning to spend time on the water to make safety their first priority. Wearing a life preserver while involved in recreational activity on the water “can make the difference between life and death,” the governor said.

O’Malley said 11 boating deaths were reported in the state last year, down from 24 in 2011. The 10-year average was 13, officials said.