A hole in a fuel line at Onset Bay Marina, coupled with an unusually high tide, caused a small amount of diesel to leak into Onset Bay this afternoon.

The minor leak occurred when someone was pumping gas, and was initially contained in the sump of an underground fuel tank, said Onset Fire Chief Howard Andersen. But high tide caused water to enter the containment area, moving the fuel into the bay.

"Once the product gets into the water, it spreads out fast," Andersen said.

There is no way of determining how much fuel spilled, Andersen said. Crews contained the leakage to a small area around the docks at Onset Bay Marina with 240 feet of absorbent "sausage" boom.

A small amount of fuel did move further into the bay, but dissipated on its own due to the sun and tide change, Andersen said.

The Harbormaster Department, Wareham Emergency Medical Services, Coast Guard, and Massachusetts Department of Environmental Protection also responded to the scene.