1. The Gemara discusses whether Chametz should be crumbled and then thrown in the sea, or whether it may just be thrown in the sea.
2. Rabah and Rav Yosef disagree about the disposal of Chametz and idols.
3. Chametz owned by a Jew over Pesach is forbidden from benefit.
4. The Mishnah derives this law (#3) from a verse.
5. The Gemara quotes many opinions regarding what prohibitions one transgresses by owning Chametz on Pesach.
A BIT MORE
1. This is a question on the Chachamim's statement in the Mishnah (21a), "He either may break it up and throw it in the wind or cast it into the sea."
2. Rabah: An idol that is thrown into the Dead Sea does not have to be broken first, but Chametz that is thrown into any regular body of water must be crumbled first. Rav Yosef: Idols should be broken first, while Chametz -- which becomes soggy when in contact with water -- does not have to be broken up first.
3. One may benefit from Chametz that was owned by a Nochri over Pesach.
4. The verse states, "And it should not be seen by you, Se'or." The Gemara later explains that this is not an actual derivation, but rather it is a penalty that one may not benefit from Chametz that he owned during Pesach.
5. The discussions refer to the level of prohibition on Erev Pesach until Pesach, during Pesach, and after Pesach.