Authorities hope to deter sea lions from boarding boats by — get this — spraying them with water.

The mischievous pinnipeds have returned to the bay after wreaking havoc last summer by trashing boat cabins and decks, swamping a vintage yacht and barking all night.

So far this spring, they've ransacked one craft and nearly scuttled a 20-foot sailboat, which was submerged to the rooftop before shipyard workers intervened, said Justin McCarthy, manager of Hill's Boat Service.

"As soon as one is up, three jump on," McCarthy said. "And it only takes four to tip one of these boats."

Seeking to avoid a repeat of last year's mayhem, harbor officials are testing a motion-activated sprinkler they hope will shoo the animals away from boat decks.

Sea lions sunbathe to raise their body temperature and don't like being squirted with cool water, said Chris Miller, the city's harbor resources supervisor.

"It's hard to control nature," Miller said. "But we're doing our best."

The high-tech effort has one observer scratching his head.

"It's funny because people don't realize the old trick is you just put a little dishwashing soap [on the deck] and they slide right off," said Hank Wiessner, co-owner of Fun Zone Boat Co.