What to expect: Built by Florida developer Henry Flagler on Key West's south shore in 1920, Casa Marina Resort is marked by tropical gardens and sculpted hedges. The main building has a sand-colored exterior with a Mediterranean red-tile roof, and newer buildings echo the grand resort style. Arrayed along a 1,100-foot private beach, the resort is 1.5 miles from the shopping, dining, and nightclubs of Duval Street.

Amenity highlights: This beachfront resort has two identically-shaped swimming pools with multiple poolside cabanas available for rental. Expansive sundecks are furnished with padded lounge chairs. An open-air pavilion between the pools and beach houses a casual bar and grill. The resort provides a pier for entering the water and an offshore sundeck for diving and sunning.

Insider tip: The beach has plenty of sand-colored umbrellas and folding chairs, and there are two hammocks, each roomy enough for two. Both are situated in shady areas and are much sought-after for afternoon snoozes. First come, first served.

What to expect: Gulf sunset views, seafood and tropical drinks, bicycle and scooter rentals, koi and turtle ponds—all this plus peace and quiet around a courtyard-garden pool—draw vacationers to this compact waterfront resort. It's located just 2 blocks from Mallory Square's famous daily Sunset Celebration and 1 block from Duval Street, with its "Duval Crawl" after-dark bar-hopping ritual.

Amenity highlights: This Hyatt offers a garden courtyard with pool, 12-person spa tub, two big hammocks, and padded lounges. A waterfront wood deck and a little sand patch in front of a pool bar are also on site. Down a flight of wood stairs in front of the pool, a tiny, pebbly beach provides access to the Gulf's green water and to a swimming raft anchored in the lee of one of the resort's two piers. Other hotel amenities include a restaurant and wireless Internet access.

What to expect: The nautical-theme lobby featuring polished wood and bold colors sets the casual ambience prevailing at the resort, which attracts adults eager to enjoy the sun and Key West's renowned nightlife.

Amenity highlights: Raised above the Gulf and providing panoramic views, a wood deck contains a good-size, heated, blue-tile pool. Sunbathers are treated to thickly padded wood lounges and green umbrellas.

Insider tip: In busy seasons and on weekends, arrive about an hour early to get a choice outside table on the pier at Sunset Pier for spectacular sunset watching.