The 'locke and key sea monster story' might be a story where the keys in the Locke and Key world are somehow connected to a sea monster. Maybe the keys are used to unlock a secret about the sea monster, like its origin or a way to defeat it. It could also be that the sea monster is guarding something that the Locke family needs to access, and they have to use their wits and the power of the keys to get past it.
Since I don't know the exact 'locke and key sea monster story', but if it's related to the Locke and Key series, the main characters would probably be members of the Locke family. They are often the central figures in stories related to the keys.
The 'Locke and Key' story is about a family that moves into Keyhouse, a mysterious mansion filled with magical keys. Each key has its own unique power. For example, the Head Key can unlock people's minds and access their memories. The story involves the Locke family's adventures as they discover and use these keys while also facing off against various villains who want the keys for their own malicious purposes.
It's a complex and mysterious tale. Locke and Key involves a family discovering magical keys that unlock various powers and secrets within their ancestral home.
The dark secrets and the haunted house elements make 'Locke and Key' a horror story. There are mysterious keys that unlock things that shouldn't be messed with, and there are often spooky apparitions and a sense of dread throughout the story.