Washington State Ferries spokeswoman Marta Coursey says the 382-foot ferry Hyak was en route from San Juan Island to Orcas Island when it collided with the 25-foot sailboat Friday afternoon.
There were no injuries reported, but the sailboat did sink in 250 feet of water.
The Coast Guard said the sailboat had a single occupant, who was picked up by another sailboat.
The cause was under investigation. Coast Guard Petty Officer 1st Class David Mosley said the ferry's captain and crew passed sobriety testing administered by the San Juan County Sheriff's Office.
The accident forced the cancellation of the 2:20 p.m. sailing from Orcas to Anacortes.