I am recommending all swimmers purchase a snorkel. The snorkel will be used during skill sessions, land training sessions, and during morning sessions,
a snorkel can have a positive effect on a swimmer’s stroke improvement by allowing the swimmer to focus on their stroke
The snorkel also allows the swimmer to straighten up and not sway from side to side keeping them as horizontal as possible in water.
Wearing a snorkel while running or doing any other dry land activity may seem a bit silly, but it creates a difficult cardio vascular environment that challenges the swimmer.
you can purchase a Speedo snorkel from Amazon:-
Just copy web address below into your browser
SPEEDO SNORKEL https://www.amazon.co.uk/Speedo-Centre-Snorkel-Grey-Size/dp/B007RWJ1I6/ref=sr_1_1?ie=UTF8&qid=1490202057&sr=8-1&keywords=speedo+red+snorkel