You don't mention your camera model, your budget nor anything about your beach photography.
Also how experimental are you? haha
I only ask because I would suggest getting a flash that has a sync port and full manual control so that in the future you can try using it off camera. The sync port isnt so important because accessories and mods can fix it; however full manual control sets apart tools from toys!
I bought myself a nikon sb-24 for use with a canon dslr for use in automatic and manual mode. works for me and my purposes. it cost me about 60$ on ebay.
I believe the above mentioned sb-600 has full manual mode and is a good fit with a current generation nikon dslr. do an advanced search on ebay to see how much theyre selling for (check the completed auctions).
MPEX developed and sells a good manual flash called the lumopro for 130$