SCUBA diving can be a great experience. Every year a quarter of a million Americans put on a wetsuit and jump in the water to explore the undersea world. If you're properly trained, scuba diving can be very safe. But there are a few common medical conditions that can make diving dangerous.

Mayo clinic doctor Jerry Sayre is a family medicine specialist who also studies dive medicine.

"Sport diving is a fantastic experience," says Sayre.

But in order for SCUBA diving to be safe, Dr. Sayre, says you need to be healthy.

"There are no hard and fast guidelines. However, medical consensus suggests that people who dive should not have diabetes, should not have asthma and should not have a seizure disorder."

Insulin-dependent diabetics could pass out underwater if their blood sugar gets too low. People with asthma could have an attack underwater, and so could people with seizures. If you're sick at all, it's best to stay ashore.

"If you have a bad cold, you probably should not dive," says Sayre.

You have to be able to clear your ears. All divers need proper training to avoid ruptured ear drums or even the bends.

"The bends is another name for decompression sickness," says Sayre.

As you descend, increasing water pressure forces nitrogen gas from your blood stream into nearby tissues. That alone isn't dangerous, but as you ascend and pressure decreases, the gas leaves the tissues. If you come up too quickly, the gas leaves too quickly, forming bubbles which can damage your muscles, joints, heart or even your brain.

"You probably should not come up faster than your smallest bubble," says Sayre.

So if you're on vacation and you want to do an open dive or a cave dive like this one, just be smart about it.

Don't go in if you're too tired, if you don't feel well, or if you've had too many pina coladas the night before.

So to make sure diving is safe for you, talk to your doctor. And enjoy the wonders of the underwater world.

Some of the main organizations that train divers include the Professional Association of Diving Instructors (PADI), the National Oceanic and Atmospheric Administration (NOAA), and the YMCA.

Again, diving can be safe if you're properly trained and healthy.

For more information, visit the Mayo Clinic Website.

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On the Web:
Professional Association of Diving Instructors

National Oceanic and Atmospheric Administration