3 Stars
The lis does stay sealed and does not let anything in when sealed properly which is great when there is a fly problem. I did use this cup in my pool and it does float however my cup kept flipping over and floated upside down for some reason could be humal error lol but at least the lid stayed sealed. If you have a carbonated beverage in this cup I wouldnt suggest having it in your pool as the carbonation keeps pushing the lid up.