After God murdered every first born male in Egypt, Pharaoh decided he had had enough. He summoned Moses and Aaron and told them to get the fuck out of Egypt. Moses quickly went and dug up Joseph's bones for some reason and led the 600,000 men and unspecified amount of women and children out of Egypt.
On the way out, he gave them more rules to follow along with giving them the go ahead to totally have slaves of their own. They followed a pillar of cloud in the day and a pillar of fire at night until they got to the shores of the Red Sea.
At this time, God decided to go and fuck with free will again, hardening Pharaoh and his top officials' hearts until they forgot all the horrible things that had just happened and decided to go bring the Israelites back by force. He loaded up his best chariots and all of his foot soldiers and raided the Israelite Camp on the shores of the Red Sea.
God came down and blew out of his nostril, apparently, a wind that was so strong it created a path through the Red Sea, which is 200 miles across and 1,500 feet deep. The million+ Israelites walked across the sea floor with walls of water the height of the Willis Tower on either side of them. They walked the full 200 miles across.
The Egyptian military decided to follow them, but God started making their chariots get stuck in the sea floor... or gravity did that... whatever. So the Egyptians tried to retreat. As soon as the last Israelite was out of the sea tunnel, God let it close, drowning the entire military of Egypt in the process.