It's night. You're in the middle of the ocean, exploring sea walls consisting entirely of vibrant life, and you see something as large as yourself, but not human, coming towards you. It's a sea lion. The enormous animal touches you, and starts playing. Your fear subsides. This is the recollection of scuba diving instructor Pat Frei from his coldest dive ever - 35 degrees - in British Columbia. When he came to the surface, it was snowing. "There is nothing like floating on the surface of the ocean, warm, happy, and shining your light up into the sky as the snow falls around you like tiny stars," he said.

That night, bioluminescence spread out all around him (certain organisms in the water emit light when disturbed, such as when a ship passes). "You find yourself surrounded by stars, and all around you in the water the plankton brightly mark your passing," he said. "It is perhaps the most beautiful experience I have ever had."

Although some of his most amazing dives have been personal endeavors, Frei spends much of his diving time teaching others how to experience this "absolutely fantastic world that no one usually gets to see." Frei teaches recreational diving at Lake Tavis in Austin, TX. His classes can have up to eight people. He spends many of his Saturday mornings swimming among catfish that are sometimes bigger than the children in the group. In the dead of winter, the water is a perfect 60 degrees, but on the same perfect day, visibility is only about 5 feet, making his efforts to keep the group together slightly difficult.

Swimming through carp and perch, Frei might lead the group over to the sunken houseboat nearby. They might also visit the remains of the shrimp boat, the barges, or the old metal swimming pool. One of the oddest things Frei has found in the lake is an old grove of pecan trees that were submerged when the dam was built. "They are huge, and you can swim from tree to tree, among the branches and such," he said, although doing so is dangerous enough that he does not take his students there.

Frei trained for his recreational scuba instructing certification 12 years ago in British Columbia, where the water is neither as clear as the Caribbean, nor as warm, but he swears it to be one of the most beautiful places to dive in the world. Most of Frei's experience has been in murkier Northern waters. Training amidst more compromising conditions, he said, just makes him a better diver. "If you go down to the Carribean after learning up North," Frei said, "they'll know where you trained."

Frei achieved his certification as a recreational diving instructor through the Professional Association of Diving Instruction (PADI), the largest global certification agency in the world. The basic open-water diver certification enables a diver to to dive privately, with equipment, up to 60 ft. Certifications then move through various levels of rescue diver, to divemaster, assistant instructor, and instructor. Instructors begin with open-water certification, but may then become certified in a specialty, such as deep-sea diving or night diving. The top level is certified master scuba diver trainer.

The highest-level divers might also pursue a career in dive instructor training to become a master instructor or even a course director. Those ready to go to the top would begin to teach some of the instructor development courses (IDC). Master instructors must certify hundreds of instructors through the course, and course directors, the highest possible level of the PADI system, teach the instructors. Only an extreme few are selected for this certification program.

The options for being a full-time diver are limited for those who don't work as an upper-level instructor, on a cruise boat, or in the Caribbean. In those scenarios, the job isn't seasonal, and the money is decent. Frei works part-time as an instructor at Ocean's Window in Texas. On the side, he does graphics and animation for a video production company. He also builds diving websites, including an original version of www.rowandsreef.com and the newly built www.freedivecanada.com.

The other option for a full-time career in diving would be to work in a dive shop, as Frei used to do. There are generally two full-time employees at dive shops, who would go out and teach about once a week, alongside perhaps five-part time instructors. The best part about this route is the free trips, Frei said. Instructors at dive shops will take it upon themselves to plan a trip, playing planner and tour guide in a liaison with a local outfit. Then, "You get to dive for free, and the hotel's free. It's a good deal," Frei said. Instructors at dive shops are often also recruited to test a new lodge for free.

Perhaps encouraged by having a background in emergency medical services, Frei loves the learning and the physiology of diving, and plans to continue his training. In Frei's ideal, "if-I-become-a-millionaire-at-40" scenario, he would love to start his own charter company.

Eventually, Frei will do his dream dive, down to the Civil War Iron Clad off the South Carolina coast. But this technical diving challenge, at extended range, goes far beyond recreational diving. Unlike recreational diving, where divers can surface any time, this trip requires divers to be down, deeper than 130 feet, for hours at a time.

Frei isn't scared easily by diving, but he admits to one uncomfortable experience. He was on a drift dive, where the water is moving, as in a river. He was 90 feet deep, missed a turn, and got blown to where he could no longer see the sea wall. He was separated from the group, and drifiting out to sea when he decided to call it a day and come to the surface.

Still, Frei doesn't generally get spooked underwater, and is adamant that diving is not a dangerous sport. "Diving gets mixed in with those extreme sports, which I don't understand, if you use your head...I get very relaxed. Being underwater never really bothers me."

The best part of his job, Frei said, is that he is "getting paid to do something you would usually pay to do." He also confessed that much of his paycheck goes back into diving, even though all his equipment is tax-deductible.

So if you're good with people, have a level head, want a career "with an injury rate close to bowling," and are not in it for the money, then dive in...and dream on!

- Leslie Tebbe, Salary.com Contributor