The book study is using the "what does the bible realy teach book". At the back, on page 174 it says this:
However, baptism is not a mere bath. It is a symbol of something very important. Going beneath the water symbolizes that you have died to your former life course. Being raised up out of the water indicates that you are now alive to do the will of God. Remember, too, that you have made a dedication to Jehovah God himself, not to a work, a cause, other humans, or an organization. Your dedication and baptism are the beginning of a very close friendship with God—an intimate relationship with him.
Might come in handy.