They had asked Professor Aizawa if they could use the academy's pool to cool off, to which he agreed, although they had time in which they could be there, they were all having fun!

Denki and Mineta ran to the pool and took a big dip, the girls were stretching so that when they were in the pool they wouldn't get a cramp, Bakugo was challenging Izuku, who he could hold his breath underwater longer... In spite of that, everyone was having fun, chatting or simply enjoying the water