Stellwagen Bank National Marine Sanctuary

It's cold and it's deep, but for divers willing to test their mettle, the Stellwagen Bank National Marine Sanctuary--a ridge that rises steeply from the seafloor off the northern tip of Cape Cod--offers wrecks and cold-water reefs teeming with temperate marine life.

"In this sanctuary, you're typically diving over rocks and ledges, looking at invertebrates of spectacular colors," says Heather Knowles, who operates the dive boat Gauntlet out of Salem, Mass. "Then, a wolf eel might jut its head out of a crevice. Docile but scary-looking, they sure get your attention." Originally created to protect the pods of humpback, minke, finback and North Atlantic right whales that gather here, the sanctuary now provides refuge for a wide variety of smaller marine life as well. From wolf eels and ocean pout, to basking sharks and sunfish, divers at Jeffery Ledge, Sanctuary Hill and Stellwagen Bank can get up close and personal with these amazing, and sometimes rare, creatures.

And that's not all. Nestled among its reefs, Stellwagen Bank also boasts a handful of wreck dives. Taking top billing among the numerous shipwrecks in the sanctuary are the Paul Palmer, an early 20th-century schooner that sank in 1913 in 80 feet of water, and the Josephine Marie, a trawler that sank in 1992, resting in 105 feet of water. Both wrecks lie at the southern end of the bank. "With excellent visibility from 30 to 50 feet, everywhere you look you'll see something," Knowles adds. "Lobsters, codfish and schooling dogfish are just some of the fish you may encounter around the wreck sites."

InDepth

The Gauntlet out of Salem, Mass., takes divers to Stellwagen Bank for $160 p.p., including lunch. Travel time is about 2 to 3 hours each way depending on sea conditions.

Experience needed: Advanced.

Conditions: Deep, 65 to 240 feet, with unpredictable currents. Water temps average between 45 and 55 degrees, and air temps are from 80 to 90 in the summer, 60-70 in the fall.

Where: The mouth of Massachusetts Bay.

When: Summer, early fall.

On the Web: Northern Atlantic Dive Expeditions at northernatlanticdive.com; stellwagen.noaa.gov.