Weapon (dagger), rare (requires attunement)
You gain a +2 bonus to attack and damage rolls made with this magic weapon. In addition, you gain a swimming speed of 30 feet and can hold your breath for up to 1 hour. While you're underwater, the weapon grants you a variety of benefits if you're holding it:
The dagger's blade extends, increasing your reach with this weapon by 5 feet.
You gain blindsight out to a range of 60 feet. You can't use this sense if you're deafened or to detect anything that isn't underwater.
You can understand whales, though you have no special ability to communicate with them in return.
Whale noises
"Ah, interesting."
"What did they say?"
"They asked for you to stop casting stinking cloud. The smell carries for miles."
"I mean, sure, but...neither of us can cast spells."
"I know."