Tom Mees, one of the original broadcasters on ESPN, the 24-hour sports cable network, drowned yesterday in an apparent swimming accident in Southington, Conn. He was 46.

The police said they were not sure how Mr. Mees drowned. They said he was with his two daughters at a neighbor's pool at about 2:15 P.M. when one of the children ran for help. Mr. Mees wife, Michelle, then found her husband underwater in the deep end of the pool and called for assistance. He was pulled out of the pool by a lawn maintenance worker and taken to Bradley Memorial Hospital, where efforts to revive him failed.

''As of right now, it's a mystery what happened,'' said Lieut. James Tortora of the Southington Police Department.

Mr. Mees was an anchor on ''SportsCenter,'' ESPN's nightly highlights show, from the cable network's inception in 1979 until 1993. Along with Chris Berman and Bob Ley, he was the network's inaugural triumvirate of anchors.

Since 1993, he had worked on ESPN2 as a hockey commentator and as an announcer for college football and basketball games and the National Hockey League draft. For the last two years, Mr. Mees had also worked as an announcer for the Tampa Bay Buccaneers football team.

A 1972 graduate of the University of Delaware, Mr. Mees got his start in broadcasting at WILM-AM in Wilmington, Del., where he was sports director. He was also sports director at WECA-TV in Tallahassee, Fla., before going to ESPN, which is based in Bristol, Conn.

Besides his wife, Mr. Mees is survived by his daughters, Lauren, 8, and Gabrielle, 4.

Thomas E Mees