I would look online at what others are asking for rent on Craigslist, trulia, hotpads, etc.. And compare your unit to those. You don't want to be asking for the the highest rent on the beach but you don't want to lose $$$ either. Keep in mind that spring and summer months are quickly approaching and those are months that more people are thinking "wouldn't it be nice to live on the beach?"
You've got a great location working in your favor in addition to there being a very LOW inventory of similar available units. Good luck to you!