The best sport in the islands is swimming, and the islands gleam with beaches, from long blond stretches of sand to tiny pebbly coves. Waterskiing, parasailing, scuba diving, and especially windsurfing have become ever more popular, though venues change from season to season. Anyone who invests in a mask, snorkel, and flippers has entry to intense, serene beauty.
The best beaches are probably those on the southwest coast of Naxos, though the ones on Mykonos are trendier. Beaches on Tinos and Andros tend to be less crowded than those on other islands in the Cyclades. The strands on Santorini, though strewn with plenty of bathers, are volcanic; you can bask on sands that are strikingly red and black.
The Cyclades are justly famous for their hiking, with the islands of Andros and Naxos being the largest and least explored. Ancient goat and donkey trails go everywhere—through fields, over mountains, along untrodden coasts. Rarely is the sea out of view, and almost never are you more than an hour's walk from a village.
Since tourists tend to visit Greece for classical sites, for nightlife, and for the beach, walking is uncrowded even in July and August. Prime walking months, though, are April and May, when temperatures are reasonable, wildflowers seem to cover every surface, and birds fly over on their migration. October is also excellent for hiking, again because the weather is pleasant and bird-watching is prime—plus, olive groves provide their own sort of spectacle when dozens of "gatherers" descend upon them to place nets beneath the trees and shake the ripe olives off the branches.
You can usually pick up maps of trails and guides in tourist offices and in local bookshops, and travel agencies on Andros and Naxos sometimes arrange group hiking trips.