KMS. U-73, Wolf Pack Leader

Submarine 2 (This creature enters the battlefield
with 2 oxygen counters on it. Remove 1 oxygen
counter: This creature is unblockable this turn)
Whenever KMS. U-73, Wolf Pack Leader deals
combat damage to an opponent, put X +1/+1
counters on it, where X is the number of
submarines you control.
Other submarines you control have +1/+1.