May children go swimming in a kiddie pool during the nine days?
Ashkenazi Children of any age should not go swimming during the nine days, or play in water, including in a bathtub or kiddie pool. Nonetheless, those who do so do not need to be protested if the children are below the age of education [i.e. less than age 3]. Likewise, in a time of great need, one may be lenient prior to the week of Tishe Beav. Sephardi children may be lenient throughout the entire three weeks and nine days including the week of Tisha b’Av.
Explanation: During the nine days, it is forbidden to swim in a pool, ocean or lake, whether to cool off or for mere pleasure and relaxation due to the bathing prohibition. Now, the question is raised regarding whether children, especially children below the age of education, must also keep the mourning restrictions that are kept during the three weeks and nine days. So, regarding cutting the hair of a child during the three weeks, the Poskim explicitly rule that the prohibition applies also to children below the age of education perhaps throughout the entire three weeks and at the very least during the week of Tisha b’Av. Likewise, regarding Yom Kippur and Tishe Beav the Poskim rule that one should not bathe a child even if he is below the age of education. Accordingly, it seems based on this that one is likewise not allowed to allow children to play in a swimming pool during the nine days even if they are below the age of education, and so explicitly rule a number of Rabbanim, unlike those are lenient without enough basis. Nonetheless, perhaps there is greater room to be lenient regarding swimming being that it is in cold water, of which there are Poskim who permit. Practically although one is to be stringent those who are lenient do not need to be protested. Regarding Sephardim, aside from the fact that they do not begin the bathing restriction until the week of Tisha b’Av, they furthermore are lenient to permit bathing in cold water even during the week of Tisha b’Av, and hence is no issue for Sephardi children to go swimming in cold water during the three weeks and nine days.
Sources: See Piskeiy Teshuvos 551:52; Chanoch Lanaar 21:4; Hakatan Vehilchosav 26 footnote 4; Nitei Gavriel 42:14 footnote 25; Poskim who prohibit: Leket Yosher p. 109; Kaneh Bosem 1:32; Chanoch Lanaar 21:4; Nitei Gavriel ibid; Poskim who permit: Shearim Metzuyanim Behalacha Kuntrus Achron 122:12 based on Yuma 78, brought in Chanoch Lanaar 21:4; Vayeshev Moshe 1:15; See also Korei Alay Moed p. 26 in name of Rav Korelitz and Rav Kanievsky See regarding not cutting hair of children of any age: Michaber 551:14; Terumos Hadeshen 152; M”A 551:38; Aruch Hashulchan 551:31; Chayeh Adam 133:18; Ben Ish Chaiy Devarim 6; Shaar Hatziyon 551:91; Kaf Hachaim 551:173 See regarding not to bathe any children on Yom Kippur: Admur 616:3-4; See regarding bathing in cold water: Rama 551:16; Terumos Hadeshen 150 “In my youth I saw people swimming during the nine days and no one protested them, nevertheless one who is stringent is blessed”; Maharil brought in Beis Yosef; Kaf Hachaim 551:186 Other opinions-Sephardim: Some Poskim rule it is permitted to bathe in cold water during the nine days. [Rambam ibid; Ramban; Ran; Shulchan Gavoa 551:13 and 48 that so is the custom in Salonika to go swimming even on Erev Tisha B’av; Yabia Omer 5:41; Yechaveh Daas 1:38; Chazon Ovadia Arba Taaniyos p. 238; Yalkut Yosef] Practically, each community is to follow their custom. [Kaf Hachaim ibid]