NOTE: This is Part 3 of a three part series on the Laws of Shabbat as it relates to staying in a hotel.
Are you allowed to swim in the swimming pool on Shabbat?
There are a few problems that we need to be aware of when using swimming pools on Shabbat.
Creating a raft on Shabbat
The Shulchan Aruch says in Siman 339 that “We do not swim in water, even in a pool in the yard, because the water can overflow and thus resemble a river." However, If there is a barrier around the pool, we are permitted to swim. Even if the water splashes, the barrier forces it back. Thus, it is more like a container, and there is no reason to decree out of concern that one will make a float. Since all swimming pools have walls, we are not concerned that a person will create a float, so it is permissible.
Placing clothes in water is considered laundry
There is a contradiction in the Shulchan Aruch. In Siman 302 Se'if 9, it says if you place a dirty garment in water it is laundry, but if you place a clean garment in water, it is not laundry.
In Siman 334 Se'if 24, it says that even if the garment is clean it is considered laundry and is forbidden. The Be'ur Halacha follows the strict opinion and says that the fact that the Shulchan Aruch uses certain language is because he copied what the Mishnah said. Many other Poskim disagree with the Be'ur Halacha, and they maintain that the Shulchan Aruch is lenient (see ספר טל אורות( מלאכת מלבן) והילקוט יוסף שבת ב' סימן שא). We can be lenient especially when a person is using a wet suit that doesn’t absorb the water.
Squeezing one’s bathing suit
The Shulchan Aruch says in Siman 301 that sopping wet clothes may not be dried near the fire. RAMA: and they are forbidden to be moved lest one will wring them out, and that is if one is particular about being wet. (Mordechai). It is forbidden to go on Shabbos in a place where one might slip and fall into water, lest one’s clothes get wet and one might come to wring them. (R"iv) The Mishnah Berurah explains that when the Rama was saying that you cannot remove garments that are wet because we are concerned he will squeeze the water from the garments because the water disturbs them. However, other types of garments that are always soaked with water won't disturb the person wearing it, and can be removed on Shabbat.
Based on that, since a person doesn’t care that their swimsuit will be wet, we are not concerned that he will squeeze water out.
Squeezing hair on Shabbat
The Gemara in Shabbat says that there is no prohibition of squeezing water out of one’s hair on Shabbat. The Rambam says that there is a rabbinical prohibition. Based on that, the Mishnah Berurah in Siman 326 quotes the Poskim that say it is a worldwide custom not to go to a mikva or river in Shabbat because there is a concern that one will squeeze water from their hair. שו"ת אגרות משה says that this custom applies only when using a river, but it is not a problem when you are taking a shower and you are pouring water on top of yourself, Therefore, a person can take a shower with cold water on Shabbat if they is disturbed by their body being dirty. Therefore, Ashkenazim cannot use a river or swimming pool on Shabbat, but Sephardim did not have this custom.
Weekday activities
The Shulchan Aruch brings in a few places this concept of weekday activities. See Siman 321 Se'if 10 regarding using a special utensil to cut cheese, Siman 335 Se'if 5 specifying that a person cannot work hard on Shabbat, and Siman 306 Se'if 7 regarding measurements of Mitzva on Shabbat, but if it is not measuring for the sake of Mitzva, it is a weekday activity.
From these examples the definition of a weekday activity can be explained in two different ways. One way is to say that if you are using a utensil in an activity that people do on a weekday, it doesn’t look good to use this utensil on Shabbat.
The second way to explain it is that if you engage in a weekday activity on Shabbat, we are afraid it might lead to actual work. However, things that being pleasure to a you on Shabbat, even if it looks like a weekday activity, is permissible, just as the Shulchan Aruch says in Siman 301 that teenagers that have pleasure from jumping and running, and looking at certain things on Shabbat, are allowed to do it on Shabbat.
Conclusion
Therefore, going into the swimming pool on Shabbat is acceptable since it a method of enjoyment and not work and we cannot say it goes into the category of weekday activities, and we cannot rebuke Sephardim who are lenient. Nevertheless, all agree that it is inappropriate to use a swimming pool on Shabbat because of many other reasons. One of those reasons is wasting precious time.