So you're getting married on the beach? Awesome. Maybe you're picturing a golden circle of sun drifting downward through a purple-orange sky as you and your soon-to-be spouse tune into the melodic sound of the ocean crashing into the sand. If not, you probably are now. That's good, hold on to that.
Disclaimer (I've never bought a wedding dress)
When choosing a dress I would first find a female friend since I'm a guy. I have been to lots of beach weddings though (like, hundreds). These are the things I've found to be true. Individual results may vary and results are not guaranteed!
The sand is gonna get you
Now back to the rosy sunset picture. There's probably some sand in that vision somewhere. Sand has an amazing ability to get and stick E-V-E-R-Y-W-H-E-R-E. Also, sand is wet and can be dirty. We have nice sand in The Bahamas but it's still not something you want on your white dress. I know the idea of a long train trailing in the sand and contrasting with the raw nature of the beach is enticing. But understand that if your dress touches the sand it will likely be wet and dirty faster than you can say "make it a double". If what you're interested in is a few amazing photos then worry not. But if you plan for your dress to remain immaculate you may want to keep the hem above your ankles.
It's the heat
Remember that sun we talked about? The sun is hot, really hot. Especially at the wrong time of day. Add the bulk of a wedding dress and it's unbearable. You've probably never been to the beach fully-dressed much less in the many folds of a wedding gown. In theory it's easy to brush this aside and decide to just tough it out. But I have to warn you, that's hard to do when sweat is flowing liberally through your very expensive makeup and hairdo. This is not an ideal time to take photographs, trust me. Think of wearing your dress in a sauna for a few minutes to help you evaluate it's sun-friendliness. Easy and breezy are good watchwords. It's also super-important to choose the right time of day, especially if your wedding is in the summer.
Getting to the beach can be a chore. Stairs and brush are just two of the obstacles you are likely to face. A long walk is also more probable than not. This is a good time to mention shoes; heels and sand don't mix. Bring a pair of flip-flops or sandals for the transition to the surf.
As usual, knowing what matters to you and a bit of planning are all you need to make your dress a timeless part of your day instead of a looming problem. Picture yourself in your dress at all your locations and transitioning between your locations. What moments matter to you most? Are you willing to pay for transportation between locations? Would you prefer a few amazing moments or lots of great candid moments? Answering these questions will help you prioritize and make your dress decisions much simpler.
It's tempting to imagine that "pride knows no pain" and that a few moments of wonderful are worth hours of suffering. Maybe. That's not been my experience though. On the photography side most folks seem to prefer natural moments of happy. Few things are more attractive than a genuine smile and those can be rare when you're not feeling comfortable. At the end of the day your wedding is a time to celebrate, not perform.