Towel(s) - only one is needed, but sometimes two is perfect.
Water bottle - don't be deceived by the fact that you are in the water...you're sweating too!
Goggles - not required, but recommended. Bring a second pair if you have one, cause you never know.
Training fins - not required, but there will be portions of practice structured around them. Have a pair that's too small?...see if a teammate could use them!
Snorkel - not required, but we will begin working in opportunities for swimmers to do some training with forward-facing or center-mount snorkels. These enable swimmers to breathe continuously, providing a different way to train.
Bag - not required, but a nice way to keep track of all (or let's be honest...most) of your belongings.