Summer's a busy season for the Tampa Bay area's scuba shops as veteran divers and newcomers to the sport get ready for tropical vacations and the upcoming lobster season in the Florida Keys.

"Everybody wants to learn how to dive as soon as lobster season rolls around," said Rocky Welch, an instructor with Bill Jackson's Shop for Adventure in Pinellas Park. "But scuba diving is not a casual sport — you have to take it seriously."

Professionals such as Welch and Bill Hardman, who writes a spear-fishing column for the Tampa Bay Times, follow a regular fitness regimen that keeps them ready for the reefs.

"The first thing I tell people is that if they want to dive, don't smoke," said Hardman, a 54-year-old former attorney who now operates a St. Petersburg scuba shop called Aquatic Obsessions. "Diving is all about cardiovascular fitness. If you smoke, your air consumption is higher and that means less time on the bottom."

Scuba diving has inherent dangers including nitrogen narcosis, or the so-called rapture of the deep, and decompression sickness, also known as the bends. But these maladies are rare compared with something that is far more common, but also potentially dangerous: simple dehydration.

"People are on vacation and they want to stay up late, have a few drinks, and they pay for it the next day," Hardman said. "Dehydration can promote nitrogen bubble formation in the bloodstream, which can lead to decompression sickness."

Hardman recommends divers of all ages and skill levels get adequate rest and drink plenty of fluids — but none containing alcohol — before diving.

"You are paying a lot of money to be there," he said. "Why not get the most out of your experience?"

Good cardiovascular fitness will also give a diver more "bottom time," scuba-speak for a longer, more enjoyable underwater experience. Divers routinely encounter strong currents that can be taxing, somewhat like hiking up a steep hill.

Veteran spear fisher and former Navy diver Ray Bourque takes his scuba fitness regimen seriously. "I spend a lot of time in the pool with fins on," the St. Petersburg investment manager said. "I also run and hit the gym on a regular basis to help stay in shape."

Bourque, 53, said older scuba divers should be especially careful. The recreational dive tables that offer guidelines for the depth and duration of dives were developed by the Navy, which used young, fit sailors as its test subjects.

"As we get older, our bodies change," Bourque said. "I have to work hard to keep my weight down and stay fit enough just to keep up with the younger guys."

Hardman echoed Bourque's advice. "Something as simple as stretching before and in between dives can go a long way to keeping you healthy," he said. "I can't tell you how many people I know have had to have knee surgery after they finished a dive and slipped on a wet deck."

Divers should prepare for their sport like any other athlete, Hardman said. "You wouldn't just run out and play a game of softball or flag football without any warmup," he said. "Scuba diving is no different — you have got to be prepared."

Terry Tomalin can be reached at tomalin@tampabay.com.