Ruling on swimming and diving deep into water when fasting

There is nothing wrong with a fasting person diving into
water or swimming in it, because that is not among the things that break the
fast. The basic principle is that things are permissible unless there is
evidence to show that they are makrooh or haraam. There is no evidence that
swimming is makrooh or haraam, rather some of the scholars regarded it as
makrooh lest anything enter the swimmer’s throat without him realizing it.
End quote. 

Fataawa Ibn ‘Uthaymeen, 19/285 

He also said: There is nothing wrong with a fasting person
swimming, and he may swim as he wishes, and dive into the water, but he must
take care to avoid letting water get into his stomach as much as he can. End
quote. 

Fataawa Ibn ‘Uthaymeen, 19/284 

It says in Fataawa al-Lajnah al-Daa’imah, 10/282 

Swimming is permissible during the day in Ramadaan, but the
swimmer must take care to avoid letting water reach his stomach. End quote.