Never mind sailing the seven seas. How about swimming them — and on your vacation?

Open-water swimming, in which swimmers navigate major bodies of water, is an increasingly popular sport — it’s been part of the Olympics since 2008 — and is beginning to attract tour operators offering “swimcations,” holidays built around oceans, lakes, fjords, and the like. Roughly half a dozen agencies are offering such packages, which can range from a daylong guided tour to excursions that stretch out over a week and include training camps, entertainment, and luxury accommodations.

SwimArt, which began offering expedition swims in 2007, has clinics and guided swims in and around San Francisco Bay for between $130 and $200 (a kayak guide is extra). Strel Swimming Adventures offers water jaunts in Montenegro fjords and lakes in the Austrian Alps. On the menu of the UK-based Swim Trek are weeklong vacations (starting at $1,100) exploring waters in Greece, Turkey, Sardinia, or Baja Mexico, and three-to-four-day  swimming tours in the Slovenian Alps or Mallorca (starting at $680).

Hopper McDonough, president of SwimVacation, a US-based open-water travel company founded in 2007, says that each year more clients are booking weeklong trips to Maine, Hawaii, and the Caribbean, and that in response to demand the outfit has added expert instruction, swimming guides, and new locations.

“Guests come from all over…Alaska, New York, Switzerland, the UK,” says McDonough, whose trips start at about $3,300 and top out at around $9,000. “We’ve had triathletes training for the Ironman, English Channel crossers, and people just getting into the sport.”

With the open-water packages, tour operators are tapping into a rigorous sport where competitors swim without aids like fins or snorkels and brave waves, currents, and aquatic life (think jellyfish). There are new open-water competitions popping up around the globe, and participation is growing. NYC Swim, founded in 1993 in New York City (members swim in the Hudson River) sponsors a number of annual events; its Little Red Lighthouse 10K swim drew 300 participants in 2012, more than double the number from 2007.

McDonough predicts a general uptick in swim tourism: “People are blown away by the beauty of the locations we choose and the freedom they have to explore the reefs and beaches,” he says. “Nothing enhances a vacation more than doing something physical each day, doing something you love, and doing something unique. A swimming vacation provides all three.”