Answer:
Without this, H2O would just be 2O
He's small but he can climb a tower.
What has a head yet it never weeps, has a bed but never sleeps, can run but can not walks, and has a bank but not a cent to its name?
Whatβs full of holes but still holds water?
How do you spell hard water with only three letters?
If itβs information you seek, come and see me. If itβs pairs of letters you need, I have consecutively three. What am I?