This is a bottle you find that has floated up on shore of the Chapter 2 island. Inside, there is a letter from D. J and another I.D. code. This I.D. code enables your Sub-C to dive in deep water.
This chapter is the first one in which you will find a Big Heart. Of course, you'll find more of these throughout the game. They add an extra heart container in your life-bar, and then refills your life.
Chapter 2 is the only chapter in the game that you'll find a Snowman Doll. It is a magic item, so you can use it the same way you can a bottle of Medicine.
Chapter 2 Weapons
The Baseball Bat you'll find in this chapter first, and then again in a few future chapters. With one swing of this, you can hit any enemies within a one block radius of your standing point. After a number of swings, the bat cannot be used again.