Don Vonk took a boat trip on the Neptune Society’s vessel the Naiad, leaving San Francisco and motoring out beneath the Golden Gate Bridge to the open sea, to scatter his father’s ashes.

But according to a lawsuit against the Neptune Society of Northern California, the trip ended with Vonk floundering in the Bay with a gaping leg wound as the 56-foot Naiad backed up toward him.

Vonk and his family members were among 27 passengers on the November 2023 trip to the Gulf of the Farallones beyond the Golden Gate, the lawsuit filed Tuesday in San Francisco County Superior Court said. With Vonk on the Naiad were the ashes of his dad, Abraham Vonk.

The Neptune Society of Northern California had no comment on the lawsuit. Its website says it offers “personalized memorial services” aboard the Naiad, and “sea scatterings” of ashes in various locations in the San Francisco Bay and near the Golden Gate Bridge.

When the boat was approaching the dock at San Francisco’s tourist mecca Pier 39, it collided “violently, suddenly, and unexpectedly” with a breakwater, the lawsuit said.

How Vonk received the injury is unclear — the lawsuit includes a photo of a gruesome open wound — but he was propelled into the water, the lawsuit said.

The Naiad backed up toward him in a “dangerous manner,” the lawsuit claimed. Vonk’s family members pulled him back on board, the lawsuit said.

Vonk’s lawsuit accused the Neptune Society of Northern California of negligence, for the Naiad allegedly motoring at an unsafe speed and failing to keep clear of the breakwater, while no proper lookout was maintained. He is seeking unspecified damages.