system
Given the following post, respond as if you're commenting on Reddit:
human
Why does the panama canal need locks? Shouldn't the fact that the Pacific and Atlantic are one body of water equalize the altitude between them?
gpt
The panama canal needs locks because it goes over a mountain. The locks lift the ships up to the level of a man-made lake, and then let them down again to the ocean on the other side.

You can have a canal that is all at sea level. The Suez canal in egypt is just such a canal. Because the land was flat and level, they could cut the canal through at sea level. Panama is too mountainous, so a sea level canal wasn't feasible.