Are you and your betrothed the kind of people who throw themselves out of airplanes for fun? Does spending quality alone time with your sweetie usually involve scuba gear or skis and a helicopter? If so, you might consider bailing on your plans for normal nuptials and make your wedding as extreme as the two of you are.
It's unlikely that the rest of your wedding party will be willing (or have room) to get into that hot air balloon with you or that any guests will be up for hiking Mt. Everest just to hear you say "I do." However, you can always select an indoor reception area that can give your guests a taste of what you're experiencing. The event room at an aquarium, for example, would be well-suited for underwater ceremonies, and a cliff-top restaurant would be a great place for your guests to hang out while you wed on the summit of a nearby mountain. You can even hook up an Internet broadcast of your vows so the rest of your wedding party can witness the event. Meet them at the party after you land, climb down or swim up to the surface.
For traditional landlubbers, get with the season on the next page.