When Galadriel and Halbrand meet the sea monster again, it also attacks everyone but the two of them. This is an interesting choice for The Rings of Power, but J.R.R. Tolkien’s books offer a possible explanation for why the creature doesn’t seem interested in Sauron. Given how he faces the monster in The Rings of Power season 2, episode 1 — which later sees him calming another beast — it’s safe to assume the series is using Sauron’s book lore to explain his survival.

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The Rings Of Power’s Sea Monster Likely Sensed Halbrand Wasn’t A Normal Man
His Power Would Have Scared It Off

The creature might sense that Sauron is a Maia — or at least something very powerful — convincing it to back down from a fight.
The sea monster in The Rings of Power seems to consider attacking Halbrand, but it likely stops when it senses he isn’t a normal man. In Lord of the Rings lore, the Maiar are innately connected to nature. The creature might sense that Sauron is a Maia — or at least something very powerful — convincing it to back down. Additionally, the sea monster is likely very old, so it may also recall Morgoth’s reign from the First Age of Middle-earth. Morgoth is largely responsible for these creatures being there, and if Sauron’s energy feels like Morgoth’s, the creature would back off.
Sauron Has A History Of Controlling Dark Beasts In The Lord Of The Rings Mythology
He Could Control Morgoth’s Creations

The Lord of the Rings: The Rings of Power Season 2 – SDCC Trailer