Is it permissible to enter a pool on Shabbat?

Hello,

It is not permissible to enter a pool on Shabbat. 

Sources: See Shulchan Aruch Orach Chaim (Siman 339:2) and Mishnah Berurah (S.K. 5), which state that if the pool does not have a rim around it, there is a prohibition to swim in it on Shabbat, because when the water is displaced and spills outside the pool, it resembles a river. This is included in the decree against swimming on water surfaces, lest one make a swimmer’s barrel. Even if the pool has a rim around it, one should still refrain from swimming in it on Shabbat, as explained in Mishnah Berurah (Siman 326:21), that the Ashkenazi custom is not to bathe in a river or mikveh at all on Shabbat due to the concern of soaking, among other reasons. See there.

Additionally, as stated in responsa Be’er Moshe Vol. 3 (Siman 56) and in Shemirat Shabbat Kehilchatah Vol. 1 (Chapter 16:39), it is forbidden to swim in the sea or in a pool on Shabbat. For Sephardim, this is also prohibited, as explained in responsa Yaskil Avdi Vol. 6 (Siman 1), and as written in Yalkut Yosef (Siman 301, p. 14) in the name of Rabbi Ovadia Yosef ztz”l, that Sephardim should likewise rule in practice not to bathe in a pool on Shabbat. See also responsa Debarot Eliyahu Vol. 7 (Siman 19) and Or LeTzion Vol. 2 (Chapter 47:32).

Best regards,
Hillel Meirs