``I'm talking zero things are alive out there,'' Miller said. ``The only way to describe it is a nuclear bomb.''

Miller and other alarmed divers say they have documented a dead zone 20 miles offshore in the Gulf waters from Johns Pass to Clearwater. This information, combined with an unprecedented number of dead turtles washing up on Pinellas County beaches this week, has divers, fishermen and scientists worried that red tide is killing more efficiently.

``Normally when we get a red tide, you can go a little north or a little west or south or someplace else and dive,'' said Ben Dautermen, who takes divers out of Clearwater on his charter boat. ``Usually it doesn't kill every single thing.''

Red tide, an algae toxic to fish and an irritant to humans who breathe its choking vapors, has hung stubbornly to Florida's west coast for close to three months. Miller and other longtime locals who make their living in the Gulf say it's the worst outbreak in their experience.

Though it's not certain that red tide killed the turtles, scientists at the Fish & Wildlife Research Institute in St. Petersburg think the toxic algae wiped out sea life, creating the dead zone Miller and other divers discovered.

The scientists' theory goes like this: Red tide cells don't like to pass through water temperature differences of more than 2 degrees. Scientists think a thermocline, or zone of cold water, formed above the warmer water at the bottom, holding the algae bloom there longer than it naturally would stay.

``So the things that would not normally be affected were exposed for longer periods,'' said Jeremy Lake, spokesman for the institute.

The toxic atmosphere worsened as dead organisms such as crabs and shellfish decomposed, consuming dissolved oxygen in the water.

Lake said the institute sent 10 biologists Wednesday for a three-day cruise to gather information on the dead zone and the status of the red tide.

Since Sunday, the Clearwater Marine Aquarium has picked up 20 dead sea turtles. Four sick turtles are being given around-the-clock care at the aquarium. The turtles, too weak to swim, are being kept on wet mats and covered with wet towels, said Dana Zucker, the aquarium's director of community relations. They are hosed down every 30 minutes.

Most of the turtles are loggerheads, but there also have been a few Kemp's ridleys, one of the most endangered types of turtles, said Janine Cianciolo, veterinarian and director of animal care at the aquarium. Cianciolo said the turtles were showing signs of red tide intoxication, but the cause of death won't be known until tissue samples are analyzed.

Reporter Mike Salinero can be reached at (813) 259-8303.