Stand on the edge of the sand and place a Bomb; unmorph (leaving Samus crouched), then press forward to enter the sand when the bomb flashes yellow for the second time. Once the Bomb puts Samus into a jumping pose where Samus is suspended mid-air slightly above the sand, press jump; then aim down precisely when the bomb begins to propel Samus upward. Move right to press against the wall before mid-air morphing (alternatively, a stationary lateral morph can work). There is a 2-frame window for when to enter the sand: if Samus enters the sand too early, she will sink slightly too far, resulting in not quite enough height to reach the tunnel; if Samus enters the sand too late, she will not get properly boosted by the Bomb explosion and will end up stuck in the sand. There is an 8-frame window for when to press jump, as it can be buffered during the period that the bomb begins interacting with Samus: if Samus jumps too early or late, she will get stuck in the sand. The timing for the aim-down press is frame-perfect: it must be pressed on the first frame that Samus begins being propelled upward by the bomb. if Samus aims down too early, she will get stuck in the sand; if Samus aims down too late, she will not get enough height to reach the tunnel. The timing for the jump is between 6 frames before or 1 frame after the down press. The amount of time that Samus holds forward after entering the sand is unimportant, as long as it is released before the aim-down.