Knock knock.
Who's there?
Abajo.
Abajo who?
I have abajo of water with me.
Knock knock.
Who's there?
Abajo.
Abajo who?
I have abajo of water with me.
Listen up, buttercup. The joke is that "Abajo" sounds like "a bottle" when you say it out loud. So the dude is saying he has a bottle of water with him. I bet you are the kinda guy who still uses internet explorer.