Our daf discusses standing in a pool on shabbat and lifting one’s feet. The question is – are we permitted to swim on Shabbat?
According to the Talmud Yerushalmi, swimming is not permissible on Shabbat because it is not within the spirit of Shabbat to go swimming. Shabbat is not merely a day in which we do not transgress the melakhot; Shabbat is a day given over to God in prayer, study and quiet rest. Swimming or gymnastics would not be in that category. The Rambam derives this notion of “Sh’vita nikeret,” or rest in a positive and even spiritually-creative sense, from the Biblical words ‘lemaan yanuach’ and the Ramban derives the same thing from the biblical word ‘shabbaton.’
The Babylonian Talmud provides a more specific prohibition upon one of three possibilities.
a) When you come out of the water you will naturally spray some of the waters or cause some of the waters to be sprayed into another domain which would in effect be carrying the water from one domain into another. This obviously would not apply within the area that there is a swimming pool within the eruv.
b) There is always a likelihood that you will squeeze out the bathing suit which is a prohibition deriving from the forbidden category of labor known as “dash” or removing liquid from a solid. This too would not apply with a synthetic bathing suit because the prohibition of “dash” only applies to something which either grows from the ground (like a fruit) or derives its livelihood from ground vegetation (like a cow, which we are forbidden to milk). The Hebrew for this is אין דישה אלא בגידולי קרקע ..
c) Rav Soloveitchik maintained that soaking a bathing suit in water – which happens naturally when one swims is included under the prohibition of cleaning (kibus) on the Sabbath, and this would apply to a synthetic bathing suit as well.
d) The rabbis were concerned lest one would make a life raft while swimming by cutting off branches from a tree nearby or something of a similar nature. This prohibition would only apply if one is swimming in an ocean or large waterway but not in a pool.
It would seem to me that taking all the above factors into consideration it would be prohibited to swim on the Sabbath.