Read these lines from the poem.

a phantom ship, with each mast and spar
across the moon like a prison-bar,
and a huge black hulk, that was magnified
by its own reflection in the tide.

what is the effect of the description of the british ship?

it reveals the threat of a new enemy.

it connects the reader to the sailors on the ship.

it suggests the enemy ships are imaginary.

it hints that there is danger coming.