As it was established by P. Lundberg, in the baptismal typology of the early Church Christ descending into the waters of Jordan is associated with the sun appearing for illuminating the universe. The Baptism of Christ is compared with the sun descending to the waters of the Ocean, and this theme is also connected with the descent of Christ to the Hell, which joins the feast of the Epiphany with the Easter.
According to P. Lundberg, it is quite natural to find a symbolism of the cross in the context of the baptismal typology, since the cross is merged in the water in the ritual of the feast of the Epiphany.
As it was established by P. Lundberg, in the baptismal typology of the early Church Christ descending into the waters of Jordan is associated with the sun appearing for illuminating the universe. The Baptism of Christ is compared with the sun descending to the waters of the Ocean, and this theme is also connected with the descent of Christ to the Hell, which joins the feast of the Epiphany with the Easter.
This sounds like it could be describing the sun god Re in Egyptian religion. Every night he died, entered the waters of the underworld, and then resurrected or was "reborn". The Egyptian pharaoh would identify with the sun god while being baptized. See this post viewtopic.php?f=3&t=5514&p=101674#p101674
Also, everyone who died was purified in water before being resurrected. The water purification ritual symbolically represented the death of Osiris in the waters of the Nile. In ritual, the Nile waters cleansed you of your sins and were associated with the bodily fluids of Osiris and the primordial waters in the underworld that the sun god entered before resurrecting or being reborn.