Where to take a spearfishing class or safety course in San Diego — freediving and blackout-rescue training, plus online options to learn before you dive.

San Diego's surface could touch 74°F this week. Here's what that means locally — accelerating kelp rot, worsening blooms, murky warm shallows over cleaner cold water — and how to still get a good dive in.

Plankton blooms are the seasonal wildcard that can beat every other number on your forecast — five feet of visibility on a glassy, swell-free day. But in California they run closer to a calendar than most divers realize. Here's how to plan around the windows.

California's water feels tropical on top and shocking at depth this summer, and that split is the whole story. Here is why 2026's warm surface lens is fueling a heavy bloom instead of clearing the water, and how to read the thermocline to find cleaner, colder visibility below.

King tides are the extreme high and low tides tied to new and full moons at perigee, and they can quietly wreck nearshore visibility. Here is how they work, which California spots suffer most, and how to plan your dives weeks ahead.

San Diego's coldest months deliver its clearest water, its warm summers turn hazy and green, and the cleanest water almost always lives offshore and at depth. Here's how to read the seasonal inversion and the permanent inner-versus-outer gradient so you pick the right day, spot, and depth.

Can you actually predict dive visibility? You can predict the odds — honestly and usefully — if you stay local and keep score. Why global “exact number” apps overpromise, and how we built ours to be honest about uncertainty instead.

Laguna's coves face southwest, which makes them especially exposed to south swell. Here is why long-period south swell wrecks shallow-cove visibility, which sheltered spots still hold up, and how to read a forecast into a go or no-go.