South Africa and South Australia have long been synonymous with white shark expeditions, but recently two spots closer to home have become the hotspots for a gander at one of the world's most formidable predators. Golden Gate Expeditions offers white shark trips to both the Farallon Islands (less than 30 miles from downtown San Francisco) and the more remote, but no less memorable, Guadalupe Island (220 miles southwest of San Diego). No reputable outfitter will guarantee a white shark sighting - the creatures are notoriously unpredictable - but in season (from the middle of September until late November), the area around the Farallon Islands is reputed to have the greatest concentration of white sharks in the world (peak white season off Guadalupe runs from mid-August through mid-December). Most choose to watch the action from a shark cage dangling just below the waterline. But you can also get a look from the boat. Rocketing up from the depths, white sharks have been known to hurtle out of the water in ­eager pursuit of the wooden elephant seals GGE uses as decoys. Cost for the one-day Farallon trip is $775 for cage ­divers, $375 for topside observers. Cost for the five-day Guadalupe trip is $2,450 for cage divers. www.goldengateexpedi tions.com, (510) 814-8256

When conditions are right, the Dry Tortugas, a sprinkling of five tiny islands nearly lost in the Gulf of Mexico, can be a birder's nirvana. Field Guides Incorporated takes birders to the Dry Tortugas via the 63-foot Tiburon, departing from Key West for the 70-mile trip. The Tortugas are renowned for a simple reason. In the spring, they are the first fleck of land that northward migrating birds encounter after one long open-ocean haul. Winging from the West Indies and South and Central America from mid-February to the end of May, worn-out birds - redstarts, purple martins, scarlet tanagers - more than 200 different species in all, fall from the sky like stones to rest on the Tortugas, their day-glo colors lighting up the islands like exotic Christmas ornaments. Cost for the four-day live-aboard trip is $970. www.fieldguides.com, (800) 728-4953