A decomposing body briefly floated to the surface just off San Francisco's shore Saturday, but evaded all efforts to fish it from the water.

Port officials were towing Drydock #1, a historic, 4200 ton structure that's now heading to China for recycling to a cargo ship near Pier 50 at 7:30 Saturday morning when the gruesome discovery was made.

According to the Chron, when a body bobbed up from beneath the steel structure, the tugboat driver stopped moving and workers tried to secure the body, but they were unsuccessful. Instead, it floated away.

Divers had searched beneath the drydock for bodies more that once, especially after a kayaker disappeared from the Bay in 2011, so officials were even more surprised than they might have normally been to see the body, which had reportedly been in the water so long that its gender was indeterminate.

Crews continued to search for the remains Saturday morning, but weren't able to find any trace of the deceased.

According to San Francisco Fire Department Battalion Chief Pete Fry, speaking with CBS5, there are a lot of factors going into why the human remains might have appeared now, and why it might be hard to find again.

“In this case, we are talking torso," Fry said. "we’re talking the idea of how long it’s been down, we’re talking about once gases are released so possibly a body could float to the surface."