You'll need your dive gear, 3-4 swim trunks, 3-4 pairs of shorts, no more than 6 t-shirts since I assume you'll be wearing staff shirts at work, 2 long sleeved t-shirts, 1 sweatshirt, 1 pair of jeans, foul weather gear appropriate for warm weather, 1-2 pairs of flip flops, personal toiletry items and a towel. You can substitute a pair of khakis for the jeans and a polo or two for t-shirts if you want to look a little more put together from time to time but it's likely not necessary. If there are any things you use on a daily basis that you absolutely must have a certain brand or product, bring enough for your entire stay since item availability can be a little sketchy sometimes. Don't forget that you're not going into the deep wilderness, there are stores if you find you need to augment a little bit.
That's it, seriously. Any more will be overpacking.
Enjoy your time in the BVI!
Rachel