- Peninei Halakha
Some maintain that one must refrain from hiking and swimming or bathing in the sea or a swimming pool during the Three Weeks, in order to limit our enjoyment during this mournful period. Furthermore, since these days are prone to calamity, one must avoid potentially dangerous activities.
From a halakhic standpoint, however, these activities are not prohibited. After all, the Sages only instructed us to curtail our joy from the first day of Av. They did not prohibit engaging in pleasurable and enjoyable activities before then. The only thing one should avoid is special celebrations, like parties, concerts, and dances. Therefore, one may go hiking and swimming and one may vacation in a hotel until the end of Tamuz. In addition, the concern about engaging in potentially dangerous activities is not so serious that one must be more cautious than one generally should be throughout the year. Thus, one may go hiking and engage in similar activities during the Three Weeks, while taking particular care to follow the safety precautions that apply to such activities throughout the year.
“When Av arrives, we curtail our joy” (Ta’anit 26b). Therefore, one must refrain from outings and recreational activities that are mainly designed to provide pleasure and joy. However, one may go on a trip or vacation that is designed primarily for educational or therapeutic purposes during the Nine Days. The same goes for swimming, whether in the sea or in a pool: If the purpose is leisure, it is forbidden. However, if one’s doctor instructs him to swim for health reasons, he may do so even during the Nine Days.
 Yesod Ve-shoresh Ha-avoda states that it is proper to avoid enjoying oneself during the Three Weeks. R. Ĥayim Palachi writes (in Masa Ĥayim) that the rabbis of his city (Izmir) instituted a prohibition against strolling through the orchards, on the beach, or along the banks of the river during the Three Weeks (quoted in Sdei Ĥemed, Ma’arekhet Bein Ha-metzarim 1:10). The other Aĥaronim, however, did not cite this stringency. It is mentioned only in contemporary works (Am Ke-lavi, p. 170; Nit’ei Gavriel 23:3, as a secondary opinion; Mikra’ei Kodesh [Harari], 5:1). It appears that this is a pious custom, which is why most Aĥaronim do not cite it. In practice, the halakha dictates that one must curtail pleasurable, joyous activities only during the Nine Days. We find the same idea with regard to consuming meat and wine and engaging in joyous business transactions: They are forbidden only from the first of Av. Similarly, there is no reason to prohibit hiking because it is dangerous. The very obligation to avoid danger is a Torah command; while we are exceptionally cautious during these days, this does not mean that we create an entirely new system of safety rules.
The same applies to swimming in the sea or a river. It is similar to hiking both in terms of the pleasure derived and the danger involved. There is a posek who is stringent about this (Mekor Ĥayim by the author of Ĥavot Ya’ir, 551:4), but many authorities permit it, as we find in Terumat Ha-deshen §150, which states that people used to bathe in rivers during the Nine Days, and no one protested. Shulĥan Gavo’ah §551 writes that the custom in Thessaloniki was to swim in the sea even on the day before Tisha Be-Av. Likewise, Yeĥaveh Da’at 1:38 states that one may swim in a pool or in the sea even during the week of Tisha Be-Av. It seems more proper to be stringent regarding swimming for pleasure during the Nine Days, not because swimming is inherently problematic, but because we must curtail our joy, as we will explain below. Nevertheless, we can derive from the opinions quoted above, based on a kal va-ĥomer argument, that swimming and hiking are permissible during the Three Weeks.
However, it is preferable, le-khatĥila, to avoid going with a large group on an outing and to refrain from scheduling a summer camp during the Three Weeks. These activities are exceptionally joyous, as they are somewhat similar to dances. Nevertheless, be-di’avad, if it is very difficult to schedule the outing or the summer camp for a different time, one may participate in these activities until the first of Av, since these activities are not really similar to dances, whose main purpose is merrymaking. Rather, the goal of an outing is to acquaint the participants with a new place and to allow them to enjoy the social setting. Indeed, it would be proper to change the scholastic calendar such that schools would be in session during the Three Weeks. This way, fewer people would go on outings or go swimming during this period. As things stand today, however, the Three Weeks is when summer camps operate and the yearly vacation takes place. Therefore, one should not be stringent beyond the demands of the law and forbid outings or swimming before the first of Av. Regarding swimming daily for exercise, which is not considered recreational, but part of a healthy lifestyle, see below, section 21, where we explain that according to Sephardic custom it is proper to be stringent in this regard during the week of Tisha Be-Av, and according to Ashkenazic custom, from the first of Av. (See Rav Pe’alim 4:29, which states that even though one who begins swimming lessons before the Three Weeks should be stringent during the Nine Days, one should not rebuke him if he acts leniently and continues his lessons during the Nine Days and the week of Tisha Be-Av. It is written in the name of Ĥazon Ish that one may swim during the Nine Days for health reasons.)