"Following Jesus" does not mean "being good", it means "being obedient." Back at the very beginning of mankind's relationship with God, we find that disobedience breaks this relationship. Restoring it, from Genesis forward, invoves sacrifice; and we find in Exodus 19 that the people are told to prepare for an encounter with God by washing. We see throughout the Old Testament the cycle of disobedience and restoration, over and over again. As the children of Adam, we are incapable of perfect obedience. And when God sent Jesus, the Messaiah, He provided in His own death the perfect and permanent sacrifice, once for all.
The other requirement for coming back into God's presence was ritual washing. Every procedure in the Torah, the ancient law (the first five books of the Bible) ends with a bath. Over the centuries, this became formalized with descriptions of basins in the Temple, and requirements for a pool with running water. One of the features of the ruins of the first-century fortress of Masada, overlooking the Dead Sea, is their mikvah, the pool, and the elaborate water channels that fed the pool there on the top of a sheer-walled mesa. To this day, Jewish communities have a mikvah, used for ritual purifications, and for the initiation of a convert to the community.
Our Gospels each begin the story of Jesus' ministry with his cousin John, the prophet who preached as he performed the ritual bath of the crowds who came to him at the Jordan River. Jesus Himself came to participate in this, not because He needed purification, but in obedience to His calling, and an example for His followers. But as the sacrifice of the Cross, which we have just celebrated in the Easter season, was once for all, our obedience to this command is also a watershed moment in our life as His disciple: a symbolic sacrificial death and resurrection with an immersion in water, coming up to a new life and new enabling through the Power of God.