The Coupeville-to-Port Townsend ferry route is down to one vessel after the Salish ran aground Sunday.

At around 12:30 p.m., the vessel made what’s called a “soft grounding,” in which it hit a sandy gravel bar but was able to free itself, according to Washington State Ferries spokesman Ian Sterling.

The ferry’s rudder was bent, which made it challenging to dock the boat and disembark the passengers.

Sterling said the rudder was probably damaged when it hit the gravel bar, but it’s unclear yet if there was any damage beforehand that caused the impact.

The incident is under investigation, and it’s not clear yet how long the boat will be out of service.

“We won’t know exactly what happened for a long time,” he said.

The run was out of service for about six hours Sunday until a tug came and towed the boat back to Port Townsend. Divers were scheduled to evaluate the extent of the damage on Monday, he said.

It’s likely the Salish will have to be dry docked, but the agency has already secured space to do the repairs.

Lack of dry dock space was a significant factor in delayed repairs to the same vessel after a soft-grounding incident last year.

“The goal here is to get the vessel back into service as quick as we possibly can,” Sterling said.

The entrance into Keystone Harbor on the Coupeville side of the route is one of the most difficult to navigate in the system, he said.

There are only three ferries within the agency that are small and nimble enough to negotiate the shallow, relatively unprotected waters.

“It’s very, very tight in there,” Sterling said. “It’s like parking a ferry boat in a garage.”

Sterling said he was unable to estimate how long the Salish would be out of service, but said it will at least be several days.