Swimming is a strenuous sport that can induce dehydration, cause fatigue, muscle cramping, and an overall poor level of physical performance. In its more advanced stages it can cause hyperthermia, heat exhaustion and heat stroke.
It is therefore vital that swimmers have plenty of fluids before, during and after training and competitions.
Read the link below regarding sports drinks!
Remember your drink bottle!
Below are some links which provide some good advice regarding nutrition and hydration.