What does Psalm 66:6 mean?

The psalmist reminds the world (Psalm 66:1) about one of God's awesome deeds: turning the Red Sea into dry land for the Hebrews' safe passage. This story is recorded in Exodus chapter 14.

The entire nation of Israel had fled from Egypt (Exodus 12:51), but they found themselves hemmed in at the Red Sea with Pharaoh's elite cavalry bearing down on them (Exodus 14:1–4). There was no possible escape; but God can do what men find impossible (Luke 1:37). The Hebrews were afraid and cried out to Lord (Exodus 14:10). They expected to be killed (Exodus 14:11). Moses reassured Israel that God intended to save His people, and that the pursuing Egyptians would never be seen again (Exodus 14:13). At the Lord's direction, Moses gestured over the sea (Exodus 14:16). Then God pushed the water back so the Hebrews could cross on dry land (Exodus 14:21–22). The Egyptians tried to follow, but God let the water return and they were drowned (Exodus 14:23–29). Moses and the people celebrated with a joyful song to the Lord (Exodus 15).