Read this stanza from "Old Ironsides." What does the word "thunders" in the third line refer to?

O, better that her shattered hulk

Should sink beneath the wave;

Her thunders shook the mighty deep,

And there should be her grave;

Nail to the mast her holy flag,

Set every thread-bare sail,

And give her to the god of storms,-

The lightning and the gale!

The storms

The cannons

The flag

The crew