All solid responses so far, I've ridden on the sand on both a beach cruiser and one of the original style mtn. bikes with knobby tires, long before the latest fat tire craze. The mtn bike is "easier" because of the gearing but as stated above you will get sand in the running gear so learn to clean it. Between cleanings you may get away with blowing it with compressed air or using a used toothbrush to knock most of the sand off. Keeping your speeds down will lessen the flinging of salt water and sand onto the bike and running gear.
If you ride near the water's edge where it's generally hard packed, full or near full pressure in the tires will work, however I've found the bike will "float" better across softer sand if you let some air out of the tires, the harder they are the more tendency they'll have to dig in. I used to carry a pump and would lower the pressure on the sand then pump them up for the ride home on the streets. And yes, anywhere but near the waters edge where it's fairly hard packed will be almost impossible. As a challenge I tried to go from the bike path down to the water's edge across the soft sand, it was quite the distance and I made it about 80% but it was a one-time challenge and took a tremendous amount of effort. I was a lot younger then!
Riding on the beach is enjoyable (there's another post here of photos by many that do it), I try to avoid running over as much of nature as you can to keep the environment folks off our backs and continue to allow beach access. I wouldn't ride in tidal areas on the rocks as it'll destroy the animals that call it home, save that for the trails. I stay strictly on the sand.
Like riding in the rain or riding in the mud, riding on the beach just requires more maintenance of the bike when you do it.
Enjoy, post some pics.
Last edited by HBCruiser1; 12-09-14 at 08:17 PM.