You could also donate your dress to a worthy organization like Brides Against Breast Cancer instead of ruining something that might bring someone else joy. It's not a Jamaican tradition - it seems to be a new thing people do after weddings.
www.trashthedress.com It's a really fun photo shoot of you and your husband in the water, laying on the sand or just somewhere unexpected. It's a growing trend with brides. I have done several in the nearby lake (not clear water like the Caribbean) and only one of the dresses was actually trashed. It was tulle and had some little rips in it. The others were all as good as new after a trip to the cleaners.
As a wedding photographer, I'll step in here..."Trash the dress" is often a misnomer...in many cases, it's just getting photos in an unexpected location and not worrying about getting it a bit dirty. It was given life by John Michael Cooper of altf.com in Las Vegas, NV. He was truly the pioneer of this and is an inspiration to many.
In most cases, the dress doesn't wind up ruined (unless that's what you want) and a good cleaning as you are likely to do anyway will restore to nearly it's original beauty, so if you want to sell or donate it, there's a very good chance you will still be able to do so.
It's a wonderful opportunity to use the dress again - get dressed up and have fantastic photos without the pressures or time constraints of a typical wedding day. If you have the opportunity, definitely go for it!
This discussion leads into exactly my current quandry...I would like to donate my wedding dress. I have found Brides Against Breast Cancer, and Vietnam Vets, but was wondering if there were any other organizations that would be interested in a wedding dress donation? I don't have anything against these 2 org's, I just want to consider all of my options....it WAS my wedding dress, you know...I want to make sure it goes to the organization I feel best about donating it to.