My husband, my son and I visited Zakynthos at the end of September, beginning of October. We stayed at Aqua Bay hotel in Tsilivi.
Honestly, you cannot find any fault at this hotel.
Nasia, from the reception, was very welcoming and she managed to find us a room at the ground floor, facing the gorgeous pools (room 120).
The family room is very spacious, modernly decorated, it has 2!!! flat screen TVs and a channel with Disney cartoons.
The terrace has comfortable cushions and the pool is right in front of the room.
The pool area was never too busy and you could always find sun loungers available.
When you buy the all-inclusive package, you have acces to the Tsilivi waterpark, which is right next to the hotel. The park has lots of waterslides for kids and adults.
The food is fantastic (you cannot stop eating those butter croissants! :)). There is a great variety and the lunch and dinner options change every day. We also went to the Greek night, organized in the water park, and it was very pleasant, with live music.
But everyone is right: the best thing at this hotel is the staff. Bella is wonderful!! She checks on you daily, speaks perfect English, she's always helpful when it comes to special requests (lunch boxes, early breakfast on the departure day etc.). Eleftheria (the name means Freedom) is a very warm person and she gave us a big hug when we left.
My advice: if you want to visit Zakynthos, this is the perfect hotel!