Kelp forest

An underwater forest of giant kelp in cool coastal seas; California's kelp forests offer cathedral light, sea lions, and dense fish life.

A kelp forest is a dense stand of large brown algae growing from rocky bottom toward the surface in cool, nutrient-rich coastal water. Giant kelp, the star species of California and other eastern Pacific coasts, is among the fastest-growing organisms on Earth, capable of adding up to 60 cm a day and reaching over 30 m from holdfast to canopy. Kelp forests also thrive off South Africa, southern Australia, and Patagonia.

Diving inside one feels like flying through a redwood grove: sunlight filters through the canopy in shafts, and the structure shelters an entire ecosystem, from sheephead, rockfish, and garibaldi to playful sea lions and, in California history, sea otters that keep kelp-eating urchins in check. Sites like Point Lobos and Casino Point on Catalina Island are classic first kelp dives.

Kelp technique is simple but specific: stay horizontal and streamlined so gear does not snag, move slowly, and if you do pick up a strand, stop and unwrap it calmly rather than twisting, most fronds snap easily by hand. Descend and ascend in the clear channels between plants, and enjoy water that usually calls for a 7 mm wetsuit or a drysuit.