Q. Dear Rov. We are staying at the cottage by the lake this Shiva Asar Betamuz, since I wake early before Alos Hashachar (day brake) to eat a meal so I can fast easier, can I then also go swimming in the lake?
A. Shulchan Aruch (O.H. 550: 2) rules that during the common Ta’anis days one may wash as he may wear shoes. However, a Ba’al Nefesh (a soul inspired individual) should avoid taking a hot shower or bath on the fast day (Mishna Berura ibid. 6 and Shaar HaTziyun ibid. 8 citing Pri Megadim).
Mishna Berura (ibid. 6) and in Biur Halocho also mentions that when possible one should be stringent excluding the wearing of leather shoes.
Poskim also maintain that one should not go swimming on the sea or a pool even on the prior night when done for joy and pleasure. (Biur Halacha quoting Pri Megodim). However when it is a health need for required exercise Poskim permit (Piskei Teshuvos ibid. quoting Be’er Moshe 3: 77).
Rabbi A. Bartfeld as revised by Horav Yaakov Hirschman, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit'a.