The best summer activity for a hot day is definitely swimming at the pool with your friends. It is a refreshing activity that will cool you down. Not only do you swim, but you can also have lots of fun playing with beach balls, playing volleyball, or even just splashing in the water. A pool party is a great way to cool off and play. You can even show off new tricks to your friends, like doing a flip or doing a diving catch into the pool. A party in the water is a great way to socialize and have lots of fun. It helps you feel cool and will be the best day ever.