It lay there in the north side water so quietly that I thought it was a log. Then I saw the whiskers. Next question: does it have ears or not? I saw no ears, only an ear hole. Answer: Harbor Seal. Not Sea Lion.
It submerged softly, without a snort or other ceremony. Seals don’t need to gulp in air before diving, as humans do. Instead, they exhale before diving, and make use of oxygen already in their blood. Their heartbeat drops from 100 to just 10 or fewer beats per minute while diving. An adult harbor seal can stay under water for half an hour, if it wants to. It can sleep underwater. I didn’t wait around to see if it would come up again.