Make the final fish. Which matches do the initial and final fish have in common?
Notice that the fish body uses 4 matchsticks in the shape of a diamond. Can you see another diamond by moving only 1 stick?
Keep the fish body intact.
Imagine moving the glass sideways. Which matchstick do two glasses have in common?
One matchstick has to be dragged a little bit.
The final glass doesn’t need to be in the same direction than the initial one.