I was 2 times in havana.I stayed both trips in Hotel plaza in downtown.
But I do not recommend you.Because around hotel food is limited. You must stay definetly near La rampa,where the hotel CUBA LIBRE.Because there are apartments for rent in there.24 hours open restaurants and nightclubs.
You cant swim in havana.But in CUBA LIBRE hotel there is also swimming pool. I went dayly trip to varadero.It was february and I couldnt swim.Because of weather.Its better you must visit havana or varadero after may.
I plan to go HOLGUIN soon because I learned weather more hot in there and beach is amazing as much as I saw on pictures .