Many of the world's hottest shark scuba diving spots also offer can't-miss topside thrills to keep your heart rate up between dives.

From a distance, it looks like a huge oil spill - but when you look closer, you can see that it's actually a massive school of fish. Samples of these Northern anchovies were taken to the lab for analysis, but scientists are still unclear on why they appeared off the coast in such shallow water.

Love historic shipwrecks? Read about the City of Chester, which NOAA recently discovered in San Francisco Bay. This Gold-Rush-Era steamship was an amazing discovery off the Golden Gate Bridge, and touts fascinating maritime history.

Bridges, piers and oil platforms are prime real estate for attracting marine life, from tiny critters to oceangoing giants. Here are some of the world's best.

Watch as divers near Souza Rock on the coast of Central California have a close call with Humpback Whales in this startling video.

Okeanos Aggressor takes you on extraordinary dives where the wild things roam. See hammerhead, whale sharks, frogfish and more in this trip report from Cocos Island.

Scuba divers flock to Shaw's Cove, Veteran's Memorial Park and Old Marineland to find a world of kelp, canyons and marine life like harbor seals.

Check out award-winning photography from BlueSphere Foundation featured artist — and Scuba Diving Magazine's 2011 Sea Hero of the Year — Shawn Heinrichs, working in Tonga.

Territory Manager Linda Sue Dingel has an encounter with squid while night diving at Veteran's Park, California. See her video of the experience.