Never heard of it? Well lots of kids have, but it can be very dangerous.

Most boaters know the basic safety rules: don't drink, wear life jackets, and watch your speed.

But few know a silent, deadly killer could be lurking at the back of almost any boat: Carbon monoxide.

"It takes less than a minute," explains firefighter and paramedic Jeff Palensky with East Pierce Fire and Rescue. "Couple breaths and you can go completely unconscious."

Saturday night, 22-year old Jenda Jones of College Place drowned in Lake Tapps. Paramedics believe it was a result of carbon monoxide poisoning, because the woman was teak-surfing on the back of a speed boat.

Teak surfing is popular among some boaters. Swimmers hang onto the rear deck of a boat while they're swimming in the water with the boat still moving. And it's a perfect place for carbon monoxide to build up.

Two years ago, that's what happened to Jay and Kelly Colbert's daughter Denise. She was swimming, also in Lake Tapps, and got a tow back to shore from a boat.

But before they reached land, Denise was overcome by carbon monoxide, fell unconscious, and drowned.

"She was an easy-going, fun-loving person," describes Jay Colbert.

The Colberts turned their grief into an education campaign about the dangers of CO poisoning by posting signs at boat launches and handing out stickers to put on boat platforms.

Some are getting the message. Boater Ryan Hansen noticed the signs the Colberts posted.

"That's what's made us aware of it. So we're pretty cautious whenever anyone's behind the boat to have the motor off," he said,

But to have another young woman die, under almost identical circumstances, is unbelievably painful.

"In some ways it's just so disheartening when we see it."

The Colberts will continue their campaign, hoping to educate boaters, one at a time; hoping to spare some other family, their grief.

Paramedics and divers who responded to the accident Saturday at Lake Tapps want to send another strong message: wear life jackets. They add that both women might have survived the carbon monoxide poisoning if they'd been wearing life jackets.