step 1

place a piston facing horizontal with a way to power it (lever or observer recommended encase the water spills)
step 2

place blocks around an empty block in front of the piston (can just be 3)
step 3

place water in the empty block in front of the piston
step 4

power the piston and the water should break dropping nothing and spawning grey squares as the particle that i believe could be the water texture are a placeholder.