what is the bottom block?

Texture Pack?

you should add a purpose to the sponge
like if it is yellow there's no water
if it is 60% blue and 40% yellow,
it is filled with water
and you should right-click it to get all the water inside the sponge out
and right-click again to absorb water
P.S: if it is in water the water absorb the max should be 2 blocks away of the sponge

wats the texture

To craft the sponge you will need: sand,seeds and bucket water.