04/26/2017 02:16 EDT | Updated 04/27/2017 10:08 EDT

Grey Whale Hit By Boat Likely Has Large Bump Behind Its Neck, Says Expert

It will be weeks before marine mammal experts know whether the whale who was likely hit will survive.

A marine mammal expert says it will be weeks before it's known whether a grey whale likely hit by a boat off the coast of Washington state on Sunday will survive.

The whale has "basketball-sized swelling" behind its neck, SeaLife Response, Rehabilitation, and Research executive director and veterinarian Lesanna Lahner told King 5. She said the injury fits with the accident.

Lahner said that while she was encouraged to see the whale diving, any pain it experienced could hamper its ability to eat and act normally.

Vancouver Aquarium head veterinarian Martin Haulena told CTV News that the swelling is a sign of a "traumatic injury."

Whale-watchers were shocked to see a small boat run over a grey whale last weekend.

Whale watchers in Puget Sound shot footage of a small boat running over a grey whale on the weekend.

Bronwen Bradshaw-Balmos, who captured video which you can see above, told Q13 Fox that people on board were horrified.

"There were lots of gasps, people couldn’t believe what had just happened," she said.

Strike was unintentional, say officials

The state’s Department of Fish and Wildlife told Q13 Fox that they think the hit was an accident and the boat’s owner is cooperating with investigators.

Grey whales are usually between 12 and 15 metres long, according to National Geographic, and weigh between 27 and 36 tonnes.

Collisions between vessels and whales are uncommon in inland waters during the day, Jake Beattie, the executive director of the Northwest Maritime Center, told KUOW.

Boaters can prevent accidents like this by being more vigilant, he said, and for looking for things that don't make sense, like "something that looks like a log but isn't."