With H-shem's help, we have begun learning Hilchot Tzitzit with the Ben Ish Chai, Hacham Yosef Hayyim of Baghdad. The sefer is translated by Shmuel Hiley and published by Yeshivath Ahavath Shalom Publications in Jerusalem 5765/2005. He calls the names of the Chapters by the names of Parashiot, so instead of Chapter One, the first chapter is called Parashath Bereshith, Laws of Ziziyoth. Please note these are for learning purposes only. For the halacha lemaaseh, i.e. for what to do yourself please ask your own Rav.
Parashath Bereshith, Laws of Ziziyoth, Page 6-7: This is a long entry so we will break it up over a few days, BE"H
10 (continued) The same rule also applies to the tallith qatan: if one takes it off to immerse oneself in a miqweh, one should not recite the berachah over it when putting it back on.
(It is written in Sefer Ha-Kawwanoth that our teacher, the Ari z'l, used to recite a berachah over the tallith qatan after leaving the miqweh (and we always accept the ruling of the Ari z'l regarding the berachoth, even when there are other opinions which rule against him). However, since the Ari z'l used to engage in lengthy kabbalistic meditations in the miqweh, he took so long over them that his immersion constituted a distraction between taking off his tallith qatan and putting it back on, so he was obliged to recite another berachah over it. We do not stay that long in the miqweh, and therefore do not have to repeat the berachah when we put our tallith qatan back on.)
Nevertheless, I rule in my work Meqabbeziel that if someone remains a long time in the miqweh, it would be correct to recite a new berachah when he puts his tallith qatan back on.
This learning should be in memory of Maran, HaRav HaGaon Ovadia Yosef, ztz'l.