Catalina Island

Two rhythms exist here. Base yourself in Avalon and the diving is walk-and-repeat: the entry, the air fills and the rental counter all sit within a few minutes of each other, so people log three or four dives at the same spot across a day and go into town for lunch between them. The alternative is a day boat from the mainland, out of San Pedro, Long Beach or Dana Point, crossing early, running two or three tanks along the sheltered coves and turning for home in the afternoon. A handful of boats stay out overnight and work the far ends of the island.

The island is rock, not coral. Boulders and ledges step down from the shoreline onto sand, giant kelp anchors wherever it finds hard bottom, and most recreational diving happens on that slope. The leeward front side, facing the mainland, holds the calm coves and stays workable in almost any forecast; the exposed back side and the offshore banks need a settled day and a crew willing to make the run. Sites differ mainly in how sheltered they are, and in how far the rock carries before sand takes over.

The draw is being inside the canopy: swimming between stipes with the light broken up overhead, then dropping under the fronds to where holdfasts grip the rock. Night diving is the other one, and shore access means it needs no charter, no crossing and no fixed departure time. Farther out the rock stands up into pinnacles and the diving turns vertical rather than sloping, which is the more interesting terrain by some distance, but a poor forecast cancels those days first, so keep spare ones in hand.

It suits divers based in southern California who want a full dive weekend without flying, and anyone logging their first kelp dives, since the sheltered entries are forgiving and the same site rewards repeat visits. Mixed groups work because non-divers have a town to fill a day with. Anyone set on warm water or big pelagic encounters will be happier elsewhere; the appeal here is structure, cool water and animals that hold still long enough to be photographed.