The Iwatobi Swim Club has a full roster now.
As they begin to practice, they run into a little trouble.
After a certain member claims that his swimsuit is to blame, the club makes a trip to buy new swimsuits.
You're allowed to use any stroke.
Man darf jeden Schwimmstil benutzen.
es decir, que puedes nadar 
utilizando cualquier estilo.
Es decir, en el que puedes nadar 
usando el estilo que quieras.
On peut utiliser 
n’importe quelle nage.
In pratica, puoi nuotare come preferisci.
Você pode usar qualquer estilo.
Значит, можно использовать любой стиль.