We visited for the day on my 30th,it was a lovely way to relax!
We got there around 10am, and it was pretty dead at that point, though it did get much busier throughout the day.
You can rent out sunloungers and umbrellas for the day (€10 each, I don’t think it’s too bad), and you can also borrow towels...
The hotel is nice (it needs some touch up on the decor) the staff are helpful especially Xazi on the desk don't be put off by the area as it is more of a local neighbourhood just around the corner is Bogatell metro station from where you can get to anywhere in the city. All in all a nice hotel.