what did the poet write to describe how the ice looked?

The ice was a pretty ominous sign. Coleridge describes it as encircling them, almost enveloping them,

"The ice was here, the ice was there,

The ice was all around:

It cracked and growled, and roared and howled,

Like noises in a swound!"

It almost seems like a frozen sea-serpand howling and threatening to crush their little ship.