To be "baptized into Moses" means to become united with or to become a follower of Moses through baptism. The Israelites were not baptized in the way that Christians were baptized in the New Testament. Paul is comparing Christian being baptized as followers of Christ with the Israelites, who became followers of Moses as they walked across the Red Sea with God leading them in the cloud. Alternate translation: "It was like all of them were baptized when they followed Moses across the sea as God led them in the cloud" (See: [[rc://en/ta/man/jit/figs-metaphor]])