Please don't be too harsh regarding this job offer. I have been to this marina and it is nicely situated. A few years ago, the marina was out of operation, or perhaps had not yet opened, but the facilities are very beautiful. When I visited the area, I liked it because it is set apart from a town and is quiet. It seemed to me that the resort was built to serve the marina.
I would reccommend obtaining a driver's liscence and a car because the distance to the nearest town, Puerto de Santa Maria, maybe a bit far for running over to the drugstore, market, or the local McDonalds, oops!, I mean cafe.
Consider that the wages include housing, bicycle transportation, 400 euro/month and tips. If this job is like waitressing in America, it will be the tips that save you, not the salary. And considering that the clientel will likely be international yaughtsmen, some of them may be forthcoming with American style tips.
(The only aspect I would like to negotiate for, given that I was interested in the position, is an apartment set a little distance from bar. I don't think I would like to be followed home by some drunk American yaughtsman.)