Thursday, December 6, 2012 | 12:01 p.m. | North Pole (inside the Silverton aquarium)

Jerry Cowley, you’re the Silverton’s original underwater Santa. What’s the story behind the ingenious attraction in the 117,000-gallon aquarium? We used to have a Christmas tree in there, but the fish liked to eat it.

A real tree? No, it was plastic. But they’d still pull all the needles off of it, and it’s not really good on their digestive tract, so we had to get away from that. I’m still finding some needles down in it, and it’s been three years.

Are you the only Santa in the tank, or do you have backups? There’s actually three of us, and we’ll rotate around. I’ve got one Santa in Hawaii right now for the next two weekends. He decided to take vacation early, so he’s not going to live that one down for a while.

How do you do “jolly” underwater? We actually have a mask on and can talk. We can ask the kids what they want for Christmas, say “Merry Christmas,” just about anything we want to say. A lot of it is just ad lib. … It’s a little harder to hear because we’ve got a beard on down there, we’ve got hair on and we’ve got a hat, besides the Santa suit and the full wetsuit. And all of it is weighted so it stays down—the suit and the beard and the hair. Otherwise it floats up and the fish attack it, too.

You’re also the Silverton’s Aquatic Safety Manager, which includes mermaid wrangling. How’d you get into that? The mermaid end of it, I learned in ’04. I actually started with them training down in Mexico. We were at Fox Baha Studios, where they filmed Master and Commander and Titanic. Where you see the Titanic go up and people falling off—we were actually in the tank that they fell off into.

Do the mermaids use full scuba oxygen tanks? They’ll go from air-line to air-line down there. … A lot of ’em are already syncro swimmers, so they’re used to holding their breath. A couple of the girls can go over two and a half minutes.

Have you ever panicked deep underwater? There have been times. As you go deeper into the water, when you get down to the 80- to 100-foot range, your brain becomes saturated with nitrogen, and it likes it, but it’s like you’re drunk. So if you’re anxious or anything like that, sometimes it can increase that anxiety. … Some of my diving has been working with a drilling crew coming through on a lateral drill, into the bottom of a lake. And when they did that it stirred everything up, so there was zero visibility. I could tell where their pipe was by feeling for bubbles.

That is, quite literally, my worst nightmare. You know what you do? Close your eyes. Your brain figures, “Oh, I’m not supposed to see anyway.” And it settles down. It was actually above a ski resort up in Utah, up above Alta, at 9,500 feet, under what they call Devil’s Castle. I worked there, in Secret Lake, for 13 days, the last part of October/first part of November. So they blew about two inches of ice off of it every morning when we got in.

It must have been freezing! Maybe that’s why I do Santa Claus so well.

Any advice for the kids planning to drop by and make requests? We tell ’em that ponies, puppies and iPhones, we have to get parent approval.