Ideal time for krias shma

In Brachos on 26a, the gemara again says that the ideal time for saying shma is just before neitz so that Shma could be said immediately before the amida. On daf 25b, the gemara said that if you're in the water and you can't get out and dressed before neitz then you should just say it in the water. The gemara there seems to be saying that you should do that just for Shma because earlier we had said that for Shemone Esrei you need to be dressed so you couldn't say that in the water. From that gemara it seems that there is a separate requirement for Shma that is not solely based on shemone esrei.

Indeed, that is how Rabeinu Yonah (on the gemara on daf 9) explains it. He says that l'chatchila one should try to say shma before neitz because of the pasuk quoted there (yiraucha). When the gemara seems to connect shma to shemone esrei it's to explain why it's best to say shma right before neitz and not earlier than that. In other words, as far as the mitzva of Shma is concerned it's best to say it after it gets light until neitz and b'dieved it's ok to say it until 3 hours. However, ideally you should try to say it right before neitz so you can do it immediately before shmone esrei.