system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do anchors work?

How do they not sink or at least weigh down the boat when they’re up? How does the boat not float away when they’re down? Do they have to catch onto something at the bottom or is their function entirely fulfilled by their weight? Do they keep a boat in one spot or do they still float within a range?
gpt
Anchors barely catch anything at the bottom, they bury into the sand a little bit. You definitely \*don't\* want them to catch a rock, then it might be hard to get it back up. The thing doing most of the work is the physics of the way the anchor chain and rope combine to pull 'sideways', instead of straight up and down.

The most important thing to do when anchoring is put out lots of chain. If you're in 5m of water, you'd typically put out 25m of chain/rope. If the weather is bad, you'd go up to 30-40m.