Solar barque

When the sun set and twilight came, he and his vessel passed through the akhet, the horizon, in the west, and traveled to the underworld.

Every night enormous serpent Apophis, the god of chaos (isfet) attempted to attack Ra and stop the sun-boat's journey.

After defeating the snake, Ra would leave the underworld, returning emerging at dawn, lighting the day again.

[4] The progress of Ra upon the Mandjet was sometimes conceived as his daily growth, decline, death, and resurrection and it appears in the symbology of Egyptian mortuary texts.

Thus, as the pharaoh was a representation of the sun god on earth, the king would use a similar boat upon his death to travel through the underworld on their journey to the afterlife.

Ra on the solar barque on his daily voyage across the sky, adorned with the sun-disk
Af or Afu (commonly known as Afu-Ra ), the ram-headed form of Ra when traveling the Duat (the 12 hours of night and the underworld) on the Mesektet barque along with Sia (left and front of barque) and Heka (right and behind of barque), surrounded by the protective coiled serpent deity Mehen .
The reconstructed Khufu ship