Two years after her son Christopher's drowning death, Dee Mullinex is on a mission to prevent tragedies like his from happening to another family.

Growing up in Grand Lake, Colorado, near Lake Grandby, the third-largest body of water in the state, Christopher wasn't a stranger to the water.

"He could swim like a fish," Mullinex told CBS News.

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But when the 31-year-old with multiple sclerosis jumped off a pontoon boat while fishing with friends on July 3, 2015 — Mullinex's birthday — he never resurfaced.

"[People] don't realize what cold water can do to you," she said. Water from the surrounding snow-capped mountains fills the lake, so it's chilly even in summertime, making it hard for a person — even a good swimmer — to function for long.

A kayaker travels across a lake in Colorado. Christopher Mullinex Water Rescue Fund

Christopher wasn't wearing a life jacket that day. If he had been, his mother believes he would still be alive.

"I always think maybe, maybe if he would've had his head above the water," Mullinex said. "That's the endpoint to this whole thing: wear your life jacket."

There were no patrol or rescue boats on Lake Grandy when Christopher disappeared, so the Mullinex family started their own search party.

With help from the Grand County Sheriff's Office, Grand Fire Protection District, U.S. Forest Service and Colordo Parks, Grand County Emergency Medical Services and family and friends, Christopher's body was recovered — four days after he disappeared.

"As we sat on the lake for days with no help — his dad, brother and close friends in their boats out searching for him — we started the Christopher Mullinex Water Rescue," Mullinex said. "Our thought process at that time is, 'This can't happen to anybody else. This is not right.'"

There are six large bodies of water in the Grand County, and not one of them has a patrol boat, Mullinex said.

They used the Christopher Mullinex Water Rescue Fund to lobby for rescue or patrol boats on all the lakes and to raise money to provide life jackets free of charge at every location.

This year, Mullinex said there will be five life jacket loaner stations spread throughout Grand Lake and the Gramby Reservoir, where her son drowned.

One of five of the like jacket loaner stations the Mullinex family has opened in their county. Christopher Mullinex Water Rescue Fund

"My goal is to see them on all the lakes in the whole state," she said.

Until then, Mullinex said her family and members of the non-profit have been traveling to schools to educate children about the importance of life vests. They even created their own coloring book with Christopher as the central character, a duck, to demonstrate what can happen if you don't wear a life jacket.

"You just try to teach the kids no matter what happens [a life jacket] gives you a chance," Mullinex said.

Mullinex said she even gives a demonstration to prove how dangerous cold water can be. She fills buckets of ice water and asks kids to put their hand in the water for three minutes. Afterward, she asks them to quickly try to put on a life jacket.

"Their hands don't work," she said. "It demonstrates that you're not thinking clearly. You can't function. It's freezing."

Not everyone will take Mullinex's advice, but she hopes the majority will. After all, it can save your life.

"It doesn't matter how good of a swimmer you are, things happen," she said.