Teams of scuba divers are hoping their pumpkin carving goes swimmingly this Halloween.

Alisa Preston, director and instructor with Rockfish Divers, is among the divers who will be carving jack-o'-lanterns under the waters near Sidney, B.C., for the B.C. Underwater Pumpkin Carving Extravaganza on Sunday.

It's an annual tradition dating back decades, she says, where teams from Vancouver Island, the Lower Mainland and the Interior go up against each other for glory.

The teams get to carve their pumpkins in the waters of their home turf, and then pictures of the results will be posted online and judged.

"Normally there's a lot of equipment with diving, but then you have the additional challenge of a pumpkin.… It's a very buoyant sphere and to be able to take it underwater can be quite an additional challenge," she told All Points West guest host Richard Zussman.

"I don't think anyone actually gets the hang of it very well. It's quite comical for anybody else that's watching."

The event has two categories: "traditional" requires all work to be done underwater, including cutting off the top and pulling out the guts, as well as the carving itself, and it all must be done with a diver's knife. "Freestyle" requires divers to only do the carving itself underwater.

Preston says anyone with dive gear can come and participate, and those without it are welcome to come and watch.

The Vancouver Island leg of the event begins at 10 a.m. PT at the diver statue at the end of Beacon Avenue in Sidney.

With files from CBC Radio One's All Points West

To hear the full story, click the audio labelled: Divers to go head-to-head in underwater pumpkin carving event