英語聽力：自然百科 佛羅里達州的溫泉（三）

Some springs would eventually emerge in saltwater, more than 20 miles offshore. Here pirates once dropped buckets overboard. It's one of the very few places on earth where the sea provides drinking water.

The warm spring waters revitalize the barren sea bed in the Gulf of Mexico and a rush of warmth allows for an oasis of life to flourish. The water surges with the arrival of sardines, hundreds of thousands of them. With the cooling of the sea water in winter, sardines seek the freshwater baths for warmth. Their presence doesn't go unnoticed by predators—amberjacks.

The panic sardines school for protection, each fish struggling to hide inside the shoal. Rapidmaneuvers and shiny scales aim to confuse. The jacks rise from below, expelling air from their gills, in an attempt to contain the sardines.

Warm waters attract more than fish. They also entice the gentlest, quietest and mostpeculiar mermaid of these waters—the manatee. For them, the springs are the difference between life and death. If the waters cool below 68 degrees Fahrenheit,manatees can die.

Manatees migrate to Florida every winter for the warmth they need, but double crested cormorants live here all year around. A manatee's life seems to be one of leisure. They spend much of the winter sleeping, surfacing to breathe without even waking up. Even the persistent pecking of sunfish, who clean them of the algae growing on their skin, don't disturb their dreams.

Sunfish are everywhere here, and that's what draws the great blue heron. When it comes to fishing, herons are masters of the waiting game. Cormorants employ different tactics. They zero in on sunfish that they know are grazing around manatees. The heron needs only to wait patiently for a share.

Its patience is rewarded. The cormorant isn't so lucky. The water's crystal clearness works against it. Fish can easily see it coming. The cormorant stirs up the mud, clouding the clear water, and launches a surprise attack. But it's the heron who ends up the winner.