Thats like asking: How can you grill burgers under water? If it were an electric grill, they would all be electrocuted and if it were a gas grill, it wouldnt work under water.
Someone said it was because starfish dont have brains, neither do Sponges, neither one have eyes and mouths as well.
If you boil this down to its essence, very little that goes on makes any sense at all - thats why it helps to be intoxicated when watching this show.