Star Wars movies have always been strong with religious motifs, and The Last Jedi is no different. Whether the viewer sees the Force as a deity-like power, the Jedi as monks or priests, or Emperor Palpatine as the embodiment of Satan, Star Wars is great at using religious symbolism. One of the religious themes I really enjoyed in The Last Jedi was that of baptism, by both water and fire.
Baptism by immersion in water symbolizes a cleansing as one descends into the water and emerges purified. It also represents a type of death and resurrection. Either way there is a change after someone is baptized by water. For example, in Revenge of the Sith Obi-Wan Kenobi fell into the swamps of Utapau after his clone troopers turned on him at the start of Order 66. He emerged from the water cleansed and changed. He became a hunted Jedi and was cleansed of the Jedi dogma and arrogance. When Obi-Wan emerged from the water on Utapau he was humbled. His humility focused his resolve, and humility is a requisite of baptism. No longer obligated to follow the Jedi Order’s strict precepts, Obi-Wan could concentrate his energy on defeating the Sith.