In theory, in MCPE, they had to bring predatory fish a long time ago. But, alas, we only have a Shark addon that adds sharks to MCPE. Well, plus, hundreds more like that. The mod is well developed in Minecraft on Android. But they turned out to be too short in Minecraft BE. But the textures are perfectly matched!
In Minecraft Bedrock Edition, you can find the shark spawn egg. Well, and in the warm seas and near corals, these representatives of enemy will wait for you. Just be careful – armor does not play any role. Sharks can easily eat Steve.