I'm sitting in my office on a Thursday afternoon when I suddenly get the urge to see water. Immediately. An ocean, a harbor, some whitewater—anything to contrast with the Kansas prairies outside my window. Last-minute-travel Web sites tout tantalizing possibilities, but now I need to know: Is it truly possible for me to be in Miami or Cancún or Ibiza by this time tomorrow—even out of a small-market airport like Wichita? Ahead on my deadlines and feeling adventurous, I open a browser and begin to investigate.

Keying in Site59.com, which specializes in turning unused flights and hotels into last-minute bargain packages, I imagine myself surfing the waves of Mazatlán, paddling around the San Juan Islands, hiking to the remote hot springs of Iceland. Perplexingly, however, my initial search yields a string of Site59 bargains to places like Omaha and Grand Rapids and Moline, Illinois. Do people really take last-minute vacations to Moline, Illinois? An ironic part of me wants to fly there for the novelty of visiting a place that sounds less interesting than where I live.

Before long, I find two promising leads for a last-minute three-day weekend, including hotel—San Francisco for $386 and Portland, Oregon, for $389. I ponder the happy prospect of swilling beers and sailing the waves of San Francisco Bay or kayaking and sleeping under the stars along the Oregon coast. Unfortunately, last-minute online travel planning is a fickle game: The San Francisco ticket automatically doubles in price if you're traveling solo and don't want a red-eye flight; the Portland ticket is gone before I can even check the details. My best bet, it turns out, is a $511 flight to Oakland, including three nights in a hotel.

Since I'm just getting started (and since Oakland doesn't feel quite as sexy as San Francisco), I try out the comparative-airfare search tool at Mobissimo.com. Punching in a few international destinations, I discover that Reykjavík and Dublin are out of my price range, but Belize is doable, at $730. With visions of scuba splashing in my head, I click through to Orbitz.com (Mobissimo doesn't sell tickets directly), where I discover the dark side of the Belize ticket: two 15-hour overnight layovers at the Atlanta airport. I calculate that I'd end up spending more time in airports and airplanes than in the water. Suddenly, Oakland doesn't seem all that bad. Returning to Site59, I discover that the $511 fare to Oakland has expired. Such is the hard lesson of spur-of-the-moment travel planning: Don't let a deal sit.

By this point I'm dead-set on going somewhere for the weekend, even if it has to be Moline. Trying not to panic as afternoon stretches into evening, I surf over to Travelocity.com's Last Minute Packages link (which is operated by Site59 but sometimes posts better deals). Here, I find a $323 flight to Albuquerque, including a three-day car rental. Unfortunately, Albuquerque doesn't have much in the way of water—that is, unless you count the three-day rain forecast from Weather.com (always a useful tool for researching your last-minute destinations). Expanding my search criteria, I discover a $422 flight to San Francisco, returning Tuesday, including a four-day car rental. Chastened by my earlier hesitation, I brandish my credit card and book it.

A day and a half later, after some frenzied packing, I spend a gorgeous afternoon sailing out under the Golden Gate Bridge with some old friends on a 36-foot sloop chartered from OCSC Sailing, in Berkeley Marina. The following day, I meet up with my cousin to see her new baby; in the evening, I take my rental car for a spin and meet friends for dinner in downtown San Francisco.

Was it worth it? On the one hand, this is not the easiest way to travel: I had to wake up at 5:30 in the morning and spend much of Friday (and Tuesday) in transit. On the other hand, it's not every weekend that I get to enjoy sea breeze in my face as I round Angel Island in the late afternoon and catch sight of the San Francisco skyline.