God has shown Himself as Father, Son and Holy Spirit. Jesus is God's one and only Son, is both fully human and fully God, lived a perfect life as an example to us, died a sacrificial death as a penalty for man's sin, rose from the dead, and reigns as Lord of creation. Jesus will return to earth again to bring an end to all that is evil and judge mankind. The person of the Holy Spirit moves in the world to convince mankind of its lost condition and lives within each believer to guide him and mold his character to be more like Christ. There are other beliefs, that while not held exclusively by Baptists, are held dearly by them and often set them apart from other faith groups.
All religions have some source of truth and authority.
For Baptists, that source resides solely in the Bible. While many denominations have a hierarchy of authority that leads to a pope, prophet or president, for Baptists Jesus exercises His Lordship directly over each congregation. Therefore, each Baptist church runs its own life under the direct leadership of Christ. This privilege is also a responsibility to serve as a priest to others in ministry and witness. As such, pouring or sprinkling water doesn't quite portray the whole picture.