The seal — smoother, rounder, conspicuously lacking the small external ear flaps that distinguish its neighbors — was spotted by at least one visitor who posted photos to r/sanfrancisco wondering if they were seeing what they thought they were seeing. They were. The sea lions tolerated it, or didn't notice, or didn't care; the dock has never been known for its strict door policy.

The distinction matters more than it sounds. Harbor seals and California sea lions are different animals at the taxonomic level of family — seals move on land in a caterpillar-like lurch, using their abdominal muscles rather than their front flippers, while sea lions can rotate their rear flippers forward and essentially walk. In the water and at rest on a dock, the difference collapses into texture: the seal's spotted coat against the sea lions' uniform brown, its rounder head, its silence compared to the sea lions' constant, percussive barking.

Sea lions colonized K-Dock famously in 1989, after the Loma Prieta earthquake cleared the marina of boats, and have returned in fluctuating numbers ever since — sometimes a few dozen, sometimes several hundred, depending on the season and the availability of anchovies and herring in the bay. A single harbor seal in that crowd is unusual enough to earn a second look, though harbor seals are not uncommon in the broader bay system.

Anyone walking the pier Wednesday would have found the dock more or less as it always looks from the observation platform: a dense, shifting heap of sea lions, some barking, some asleep, the smell carrying even on a light wind. Whether the seal was still among them was not immediately clear.