Divers searched the shattered Coast Guard buoy tender Blackthorn at the bottom of Tampa Bay yesterday in the hope of finding survivors from a collision with an oil tanker, but feared 17 crew men officially listed as missing were dead.

If no survivors were found, the death toll would be 23 -- the worst peacetime accident in Coast Guard history.

"The ship's lying on its port side at the bottom of the channel with the hulll facing skyward. There is debris all over the place," said John Kettel, one of the nine rescue divers who searched the wreakage for bodies.

Twenty-seven of the Blackhorn's 50-man crew survived the Monday night collision with the 560-foot tanker Capicorn near the Sunshine Skyway bridge in the main ship channel from Tampa Bay to the Gulf of Mexico.

Six bodies have been recovered. The 17 missing crewmen were feared trapped in darkened passaways or compartments or washed out to sea.

The Capricorn, owned by Apex Marine of Lake Success, N.Y., and the 180-foot Blackhorn collided with a "horrendous, grinding sound" that tore a gaping hole in the side of the buoy tender and sank it like a stone.