A dozen rays jostle for attention each time Carl Perkins enters the tank, their flat bodies undulating on the exhibit floor.
"They all get right around my feet like puppies and nudge me as if to say, 'Feed me first,'" said Perkins, the new principal of Centennial High School and a volunteer diver at the National Aquarium in Baltimore.
The six species of rays, some of which can grow to be 7 feet across and weigh close to 500 pounds, are "a lot of fun," he said. Three dozen of them inhabit the Wings in the Water exhibit, sharing the space with two sharks and a turtle.
And what could be more harmless than playful animals that aren't known for aggression, right? Not true, said Perkins.
"Danger is inherent when you're in the tank with the rays," the 57-year-old Clarksville resident said. He noted that the animals' whip-like tails have been clipped for safety's sake, a precaution taken by aquarists long before a stingray's poisonous barb killed TV celebrity and wildlife advocate Steve Irwin two years ago.
"The reason we divers don't get hurt is our understanding of animal behavior," said Perkins, who also feeds sharks, turtles and fish. "And we don't indulge in any ill-advised stunts."
Behavioral knowledge plays a large part in his role as a principal, too. While this year marks Perkins' first venture into high school administration after 17 years at three middle schools, he sees more similarities than differences.
"I'm still responsible for the emotional, social, psychological and physical aspects of the students when they're here," said the 30-year veteran of the county public school system, who began his career in Howard County as a teacher at Centennial.
"I will give my high school students the exact same message [as middle-schoolers]: that the staff is here to give them guidance and provide a strategy for success," said Perkins, a Baltimore native who earned his undergraduate degree at the former Towson State University. "The only difference now lies in how I deliver that message."
Perkins indulged his lifelong passion for swimming by becoming a certified diver in 1977 and then volunteering at the aquarium the year after it opened in 1981. Soon after he signed on, he had his first and only close call.
"I picked up a dead fish to feed to a bonnet shark, and I guess I held onto it a little too long," he said. "The shark nipped me on my right hand to get at the food - but it wasn't too bad."
The principal has not had a real nemesis in the decade since a 160-pound hawksbill turtle named Pita died. Pita - an acronym for "pain in the ankle" - liked to bump the divers in the head and nip at their feet, he said.
But there have been plenty of marine animals with their own quirks to fill the void.
A rescued green turtle named Calypso navigates the tank minus her right front flipper, which had to be amputated after an injury, and loyally follows the divers around. And Zoe, a blind zebra shark that is fed by aquarists, swims playfully between the volunteer divers' legs as she tries to score a helping of another animals' food.
The creatures' ploys for attention are what separates aquarium diving from deep-sea diving, said Jennifer Bloomer, media relations manager for the acquarium.
"These animals seek the divers out instead of fleeing from them," she said. "There's so much more interaction here than in the open ocean."
Watching the animals' antics unfold underwater is one of the main attractions for visitors, who number 1.5 million annually, Bloomer said.
With more than 2 million gallons of water in tanks throughout the building and three dozen animals and many varieties of fish to feed twice daily, the aquarium maintains a staff of 230 volunteer divers who come from as far away as Virginia to assist the 50 staff divers, said Chuck Eicholz, dive safety officer.
"It takes a unique person to have the dedication to volunteer here," Eicholz said, though he added that many divers quickly become addicted to the work. Perkins is one of the best they have, he said, and he has one of the longest consecutive volunteer diver tenures at the aquarium.
The 500 fish, 36 rays and two sharks in the tanks where the volunteers work are fed smelt, squid, clams and shrimp. Calypso is served a vegetarian diet of romaine lettuce, broccoli and frozen peas, as are some fish. In the aquarium as a whole, there are 16,500 specimens of 660 species of animals, including dolphins, birds, reptiles and more sharks.
While nothing can shake Perkins' enthusiasm for diving, which he has done in the Atlantic, Pacific and Caribbean, he admits that his desire for underwater adventure has abated somewhat.
"I used to dive in turbid water over 100 feet deep - that's a lot of danger and a lot of stress," he said. "You must rely solely on your gauges because visibility is only 11/2 feet out in front of your face."