To make this faster and easier, get the yellow pikmin first. Then go to the "Impact Site" level and go into the part past the box with the number 10 on it. Have the yellow pikmin pick up the bomb rocks on the other side of the box, and use three of them to knock down the white wall. Once you go inside, stay close to the sides as not to drown your pikmin. To the right, around the corner is a clam type thing with a pearl in it's mouth. Stand next to it and put your site in it's mouth just next to the pearl. Grab a pikmin with a bomb rock and toss it it. It should land in, run out and throw it's bomb rock. Do this twice to kill it. Have them take it back to the onion and you get about 50 pikmin seeds!!!