Grab the Light Block at Point 1, then hit the ? Switch to make the floor disappear. As you fall, grab as many coins as you can.
Wait for the Bulbers to swim toward you and light the way ahead. As they do, watch for the boulders that fall from above and quickly swim past the Stone Spikes’ attacks.
Go through the pipe at Point 4 to find a small room with several coins and a Spiny Cheep Cheep!