Chain Link Chamber
Past the continue barrel there are two Klumps which shoot Kannonballs
down a pair of chains which you must climb. Part of the way up
those two chains, there is a single banana on the right-hand wall;
jump through the wall at that point and head to the right.
About 1/4 of the way to the continue barrel, there is a single
vertical chain with three Krooks. Kill the uppermost Krook. Behind
him is a Kannonball. Jump down and across the shaft to the right
(carrying the Kannonball) to kill the middle Krook; behind him
is a Kannon.
After climbing the two chains (where the DK coin is located),
cross the the right and up a bit. You can jump through the left
wall to sit adjacent to the two Klumps. Kill them and go through
the door to the left.