The episode centers on the birth of Ryn's daughter, Hope. Because the baby was carried by Meredith, a hybrid, there are severe medical complications. Ryn and Cami must intervene to ensure the baby reaches the ocean quickly for her survival.
As indicated by your file name, the series was available via Amazon Prime Video. Siren.S03E04.Life.and.Death.PL.1080p.AMZN.WEB-D...
The "PL" in your file title suggests a version with Polish subtitles or dubbing. The episode centers on the birth of Ryn's daughter, Hope