The tagline for NBC’s demanding obstacle course Spartan: The Ultimate Team Challenge is “no one triumphs alone.”

You don’t have to underscore the importance of that slogan to divemasters Sarah Tingey and Rachael Priest, who plan to dive the three highest-altitude lakes in the UK within 24 hours, the first women to attempt the daunting Three Lakes Challenge, completed in 2007 by Andy Torbet and Monty Halls. In late April, Tingey, who is 27, and Priest, 25, will travel first to Scotland and then to England and Wales, undertaking a grueling hiking and diving — not to mention driving — schedule to achieve their goal. They have dubbed their venture Mission High Water.

“We will start the clock in Scotland and it won’t stop ‘til we get back to the car safely in Wales,” says Tingey. The teammates will hike up a mountain to the first lake, get kitted up, dive for at least 20 minutes, de-kit, hike down, drive to the next location, and repeat twice more — all in one day’s time.

While the women are preoccupied with handling the logistics, they are also targeting a greater objective: raising much-needed funds for Dorset and Somerset Air Ambulance Service. In the English countryside, where transportation is limited, the women consider themselves lucky to have airlift services. DSAA not only helps injured divers and hikers, but also everyday local people, from infants to the elderly.

“We would be lost without these services,” says Tingey. “Through our work in the diving industry and living in rural areas, both Rachael and I have experienced firsthand the importance of rapid emergency medical care. When time is critical, a helicopter can make the difference between life or death.”

With no government funding, the air service relies solely on donations. A single DSAA lift costs nearly $3,300. Through Mission High Water, the women hope to raise enough money to fund at least one helicopter mission.

The duo is training hard, walking long distances (up to 10 hours a day, along with incremental cold-water swims), lugging weighted backpacks to prepare for arduous mountain hiking.

Used to diving in drysuits with twinset tanks, the women will adjust their gear to make the treks easier. To complete the Three Lakes Challenge successfully, the women must carry all their gear and be self-sufficient while hiking and diving.

But what they’re most concerned about is what they can’t control — weather and traffic.

“Hopefully we won’t end up trudging through too much snow,” says Priest. “But I am most nervous for the driving. We will try our best to avoid traffic, but I don’t want it to be too horrendous that it slows us down, stopping us from achieving our goal.”

“The only thing to do is prepare as well as we can and expect the worst,” adds Tingey.

If all goes well, however, the women are excited for the adventure’s scenery and, of course, the finish line.

“The sunrise at Coire an Lochain [Scotland] as we come up from our first dive and descend down the mountain could be quite stunning,” says Tingey. “I also think the celebratory chocolate bar and cup of tea in the car park at the end will be a moment I will cherish forever.”

To donate to Mission High Water, click here.