Captiva Island, FL
Sure, it's a tad cooler here in October than, say, in June, but a sweater or light jacket should nullify that. The payoff? Quietude, miles of peaceful beaches, accessible tennis courts, and no waiting at the waterfront restaurants. The entire island measures five miles by about a half-mile, meaning you can kayak the mangroves in the morning, cycle the gentle roads through vibrant vegetation, take a long afternoon nap, and still make sunset cocktail hour on the beach.

Plettenberg Bay, South Africa
This series of arcing beaches, known as the Jewel of the Garden Route, draws not only an eclectic mix of people but also a wide array of sea life, including the rare Southern Right whale and other whale species (viewable from hillsides all around town). The mountains just inland bloom with wildflowers in spring (September to November), leading into the languid days of southern-hemisphere summers.

Mauna Kea Resort, Big Island, HI
Despite the fact that this beach is held hostage in a massive, expensive golf resort, it remains a treasure to behold—a near perfect, subtly curving expanse of creamy sand, lapped by light blue waters that seem to always be at just the right temperature for your mood. The sea bottom is the same cozy sand, except at either end of the roughly half-mile beach, where rocky outcroppings provide dizzyingly solid snorkeling. Once you find your way in (they allow a certain number of day trippers in per day), soak it all in, including at least one rum drink at the pool bar. (www.maunakearesort.com; 1.888.9.PRINCE)

Jake's, Treasure Beach, Jamaica
This off-beat boutique resort on Jamaica's little-touristed (and desert-like) southeast side is all about personality: Each of the 29 rooms is decorated differently, and all of them preserve a romantic privacy worthy of honeymooners. The funky bent, punctuated by a seaside yoga platform and the character of a real local fishing community, makes Jake's a favorite of artists and writers. (www.islandoutpost.com/jakes; +1.876.960.8134)

The Beaches of Anguilla
With more than 30 elysian beaches on this low-key island, we could recommend two wave-side paradise spots a month all year and still have some left over. Instead, why don't you go, pick your favorites, and send us a postcard? Among the best ways to access said sands is by mountain bike along Anguilla's rolling jeep roads. Perhaps the top adventure is pedaling to Little Bay, where the beach is attained by climbing down a rope off the ruddy cliffs, below which sapphire seas and dazzling snorkeling await.

San Blas Islands, Panama
If you didn't think a South Pacific daydream existed in the Caribbean, you need to check out the San Blas Islands. Hundreds of palm-tufted pearls of white sand seemingly float on the glowing blue sea. The Kuna Indians live here, sometimes only one or two to an islet, and they are as mellow as they come. Visitors stay on a main island and take motorized canoe shuttles out to the smaller islands, clutching a dollar or two for the requisite visitation "toll." Also bring sunscreen, snorkel, mask, fins, and perhaps even a GPS to prove to yourself you really are in the Caribbean.

Placencia, Belize
Some places have dreamy beaches or dense exotic jungle or lively cultural scenes. And some places, like Placencia, have it all: 16 miles of beach, accented by fantasy-fulfilling offshore cayes; a shimmering aqua lagoon, serving up snorkeling for all abilities; loamy rainforest, ripe for exploration; some of the world's best scuba diving on the Latin American barrier reef; and the richness of Mayan, Garifuna, and Creole heritage that dates back hundreds of years. If that's not enough, how about the 4,000-foot-long "Placencia Sidewalk," which hold the Guinness world record for being the Longest Main Street in the World?

Buck Island Reef, Saint Croix
On the scenic and purity scale, you would expect a lot from a beach that's part of a national monument 1.5 miles off of the mellowest Virgin Island. And Buck Island delivers: Long stretches of exposed beach lay at the foot of green hills edged with sky-blue seas. Unsullied reef with deep holes and grottos serves up some of the best snorkeling and diving in the Caribbean. Accessible by day boats; bring all you need; there's not much for service out here (but hey, that's why you came).

Hanalei Bay, Kauai, HI
This is the Hawaii of post cards, a huge crescent forming a wide grin on the lips of a luxuriant bay. Bathe in the warm translucence of the sea or, if the surf's up, paddle into one of Kauai's classic beginner waves. Then head into Hanalei, one of the mellowest tourist towns in the islands, for a yoga class, a fresh seafood dinner, or just to hang out and gaze up at the frequent rainbows spawned by the rainforests in the hills above.

Emerald Bay (Pantai Teluk Belanga), Malaysia
Paradise found. On the privately owned island-resort of Pangkor Laut Resort, this Elysian arc of bullion sand and glimmering turquoise water will leave you swooning. Look for wild tropical birds and other wildlife in the ample jungle surrounding the resort. Or look out to sea, or for the gracious and efficient waiter with your next cocktail. Just don't look at your watch.