Praia do Dentista, Angra dos Reis
Good For: Sports / Sun
From December through February, the tourmaline-green waters of Praia do Dentista swirl with the bikinied Cariocas who've made Angra dos Reis one of the country's chicest destinations. Located on Gipóia, the second-largest of Angra's 365 islands, Dentista can be accessed only by boat; indeed, on busy days, dozens of motorboats, sloops, and speedboats make its waters an impromptu marina. Here, everything—time, responsibilities, reality—feels suspended, sometimes literally: The crescent of white sand is so narrow that you'll spend more time bobbing in the warm, jewel-bright waters than lounging on the beach. The only other diversions are people watching, paddling to the floating no-name food-and-drinks shack, and watching the brief but spectacular equatorial sunset.
The 411: Overnight at Pousada Naturalia (see Blue Lagoon, above), on neighboring Ilha Grande. Or stay on the mainland, in the lovely little colonial town of Parati, where the affordable, unassuming Pousada Pardieiro makes a good base for explorations up and down the coast (55-24-3371-1370; pousadapardieiro.com.br; doubles, $134—$158); while there, don't miss the atmospheric Porto Restaurante, which serves modern interpretations of classic Brazilian fare (14 Rua do Comércio; 55-24-3371-1058; entrées, $13—$27).
When to go: If you're a party animal, Christmas and New Year's; otherwise, stick to early February, before the rains set in.

Lopes Mendes, Angra dos Reis
Good For: Scenery / Sports / Sun
Like most things that are worthwhile, reaching Lopes Mendes is work; in this case, a steep and muddy 20-minute trek from the village of Palmas, on Ilha Grande (see Blue Lagoon, above). But the payoff is pure heaven: a two-mile, caramel-colored crescent, and water a remarkable opalescent blue. With its consistent, clean breaks—in March, waves top out at 3 feet, but in winter they can reach 13—Lopes Mendes is a treat for surfers of all stripes. All others should head to the west end of the strand, where breaking waves explode against massive outcroppings; one rock in particular is pitted with dozens of neatly arranged pockets, each of which holds, Advent calendar—like, a glossy black sea urchin. There is no development here—just you, the ocean, and the insistent crashing waves.
The 411: Pousada Naturalia (see Blue Lagoon, above) is the most convenient accommodation.
When to go: The biggest waves arrive during the equatorial winter (June—Aug.); those looking for gentler surf should travel in summer (Dec.—March).

Praia do Siriú, Garopaba
Good For: Scenery / Sports/ Sun
Just before you round the final bend on the road to Siriú, in Santa Catarina State, you come upon a field of dunes up to 130 feet high, whose sudden and surreal appearance is heightened by the scene of timeless normalcy across the street: a lovely, lush forest dotted with wood-frame houses and alive with the sounds of cowbells, roosters, and the locals' murmured conversations. From here, you hear Siriú—a protected state park with few houses and no commercial development—before you see it, its powerful, complaining waves breaking against a lonely windblown shore. The water is gray and cold and so thickly foamed that it looks beery, and the low hillocks behind it are hairy with pale-green sea grass. The waves arrive in long, unbroken pleats, with kids and sleek pros alike attempting to master them on longboards. Sunbathers can head to the beach's northern end, where at the foot of a seagrape- and bromeliad-strewn hillside sit a cluster of fat, smooth rocks, like sea lions lounging in the sun.
The 411: The most reliable accommodation is a 20-minute drive from the beach: Fazenda Verde do Rosa, a 36-bungalow property built of local materials (55-48-3355-7272; fazendaverdedorosa.com.br; doubles, $56—$180).
When to go: The area is liveliest from December through February, but serious wave riders can test their mettle from June through August.