The Gemoro says (25b) that the Mishna re saying Shema in the Mikva before Honetz HaChama need not be like Rebbi Eliezer, but might be speaking of one who says shema Kevosikin.
I was very puzzled about this, since the Gemoro said earlier that Vosikin say Shema before sunrise, then are Somech Geula LiTefilla, and say Shemone Esreh immediately after sunrise.
Question 1) When will this man daven Shemone Esreh!?
Question 2) When does this man say Birchos Kerias Shema?
I did see Rabbenu Yona (who says that the man will say Shemone Esreh later, but Vosikin say that there is a lechatchila time to say Shema before sunrise, even if he is not Somech Geula Litfilla), but I think other Rishonim hold that the main point of Vosikin is to say Shemone Esreh immediately after sunrise (and therefore one must say Shema before sunrise) - how do they understand this Gemoro?! (If the man comes out of the mikva, gets dressed, and then davens, he might as well have come out of the mikva first and then got dressed!)
Kol Tuv
Mark Bergman, Manchester, UK
When the Gemara establishes the Mishnah like the Vasikin, it is referring to the Reisha (where he manages to get out of the Mikvah, and get dressed before sunrise, and), where he will indeed recite the Sh'ma before Hanetz and Daven the Amidah after it. The B'rachos are not a problem, because Davening ka'Vasikin overrides the B'rachos in a case of emergency, such as this one (like it overrides Davenning with a Minyan and putting on Tefilin - see Biy'ur Halachah Si'man 58 DH 'u'Mitzvah min ha'Muvchar').
You referred to the Seifa - reciting Sh'ma whilst still in the Mikvah. This has nothing to do with the Vasikin, who will agree that it is more important to recite the Sh'ma before Hanetz, than placing Tefilah next to the Sh'ma; and by the same token, it too, is more important than reciting the Berachos (which in any event, pertain to the Shemoneh-Esrei, at least according to some commentaries).
By the way, most of what I wrote I took from the very Rabeinu Yonah that you referred to.
Kol Tuv,
R. Eliezer Chrysler