Weapon Idea: Sword of the Deep

The Sword of the Deep would be a rare relic/weapon of sorts, being found either in shipwrecks and ruins, or a potential drop from Elder Guardians. It could cause enemies in water to sink for a few seconds, or increased knockback against them, making it useful while exploring oceans. It could have a base damage between iron and diamond, and perhaps gain a damage boost when underwater. It could cause cool bubble particle effects in water when swung, to add a bit of coolness.