Product review (5 stars): Put the plug in a bowl of hot water first and it goes in so easy!
Bought this for my one year old grandson who loves it. My son put it together but couldn't get the plug in. After I tried the butter knife trick and using dish soap with no luck I heated water in a bowl in the microwave then put the plug in the hot water, took the bowl outside and the softened plug went in so easy it was amazing! After filling with cold water the plug became more rigid and absolutely no leaking.