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human
ELI5: Why Do Big Ship Pull Water From Shore?

When I was growing up near the mouth of the Detroit River, we always could tell when a large ship was approaching.  The water level in the canal behind our house would lower significantly, then rise again as the ship passed.

Today I saw a video where a cruise ship sucked the water away from Ft. Lauderdale beach.

Why does this happen?
gpt
These things are moving so much weight that when they're moving they push tons and tons of water behind them. That creates a bit of an up-lift behind, and a depression in front. The water around the depression moves to fill in the depression which pulls it away from the shoreline.

I passed an oil tanker in a channel near the Gulf of Mexico that was going in toward a port and it evacuated an area of water probably 300 yards across as it went by. We had to park the boat near the shoreline and as the tanker passed our boat was left 100 yards from any water for probably 10 minutes before the water finally returned to normal.