Q. One who everyday is tovel in the mikva, and owns a cottage where he uses the lake for his daily tevila before davening. If a proper eruv is placed on the lakefront of the cottage and the eruv of the property covers some of the lake area too (it was placed on metal poles on two parallel docks going into the water and a third cable was placed properly on two poles at the end of the two docks), can one be tovel on Shabbos in the lake, if no mikva is available?
A. Shulchan Aruch (O.H. 356: 1) and Mishna Berura (1,2) require proper mechitzos (fences and not just cables or tzuras hapesach), in the water area. Namely, they should be at least ten tefachim high and at least a tefach should be inside or outside the water. Horav Akiva Steinmetz Shlit’a mentioned that due to the waves and likely tides, the mechitzos, should be placed on the outside side of the docks, so one may carry also on them and be high and deep enough, that at least a tefach should always be inside and outside the water level. A similar mechitza should also be placed at the far side, and joining the two docks.
However, one may use an eruv made of tzuras hapesach for the dock itself, that extends and connects to the property eruv and use it for eating there during Shabbos.
Horav Shlomo Miller’s Shlit’a opinion is that it is simpler to walk dressed with a bathrobe close to the lake, crossing the eiruv or tzuras hapesach he must have around his property. Since he is not carrying the bathrobe but wearing it. Place it down on the shore close to the water and proceed to immerse in the lake. When he exits, he should be careful to do it slowly so the water will drain from and his body will be mostly dry. He the can pick up his robe and wear it before he crosses into his property eruv.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a