What would happen if the distance between the earth and the moon decreased?

If the distance between the Earth and the moon decreased,
then a few of the changes would be ...

-- The moon would appear bigger in the sky than it does now.
 
-- Then the moon would revolve around the Earth faster/more often.

-- The moon would go through its cycle of phases faster.

-- Solar and lunar eclipses would both happen more often.

-- High tides would be higher.
   Low tides would be lower.

-- There would still be 2 high tides and 2 low tides roughly every day.
But they would be spaced by less than today's average of 6hrs 12min.

--the moon will revolve around the earth more often and faster, eclipses will occur more often both solar and lunar, The  moon will appear bigger in the sky, there will be higher tides as well as lower tides

The gravitational force between earth and moon will increase.
by F = GMm/r^2
F is inversely proportional to r^2
when r decrease, F will increase.

The gravitational force of the Moon disrupts this balance, pulling a tidal bulge of water with it as it orbits our planet and as the Earth rotates, it too causes a tidal bulge on the opposite side. ... Low tides would be lower and high tides would be higher and any low lying coastline would be flooded.

The moon would appear much larger in the sky. the moon directly affects the ocean tides. If it were much closer, the ocean would rise and flood coastal areas. If the moon were much farther away from Earth, then the ocean tides would quit and the oceans would stagnate, killing all plant and marine life.