Question:

Can one mourning a parent swim after the shiva period/ during the 30 day or 12 month?

Answer:

During shloshim the avel should not go swimming if it is for pleasure purposes, however if it is for medical reasons, of because he is a lifeguard etc. then it is permitted.

During the 12 months the avel may go swimming.

Sources:

Kol Bo pg 356, Kitzur Shulchan Aruch 209-7, Nitei Gavriel Aveilus vol. 2 8-3, Ohel Yackov Aveilus 4- 48,49.

Rabbonim of the Beis Hora'a