Need Help: Cistern - Wooden Bridge

[Actionhero]

hello,

my english is not perfect, i'm from germany, but i need help (savegame or hint).
i'm in the cistern with the wooden bridge on the rusty chain. the walkthrough that i found says:

Continue moving along the platform and cross the bridge. After crossing
it, to the left you'll find a raised bridge. Go near it and check it out.
It says it's attached to a rusty chain! Simple solution, we have to hit
the chain with something hard! Find a rock nearby and throw it at the
rusty chain holding the bridge up. The rock is actually just where the
bridge is. There are some more rocks on the platform if you miss.

but i can't hit this damn chain...