Why the sea is compared to a dog?

The poem:

The sea is a hungry dog,

Giant and grey.

He rolls on the beach all day. the waves roll on the beach all day

With his clashing teeth and shaggy jaws

Hour upon hour he gnaws

The rumbling, tumbling stones,

And 'Bones, bones, bones, bones! '

The giant sea-dog moans,

Licking his greasy paws.

And when the night wind roars

And the moon rocks in the stormy cloud,

He bounds to his feet and snuffs and sniffs,

Shaking his wet sides over the cliffs,

And howls and hollos long and loud. the sea makes a crashing and howling sound.

But on quiet days in May or June,

When even the grasses on the dune

Play no more their reedy tune,

With his head between his paws

He lies on the sandy shores,

So quiet, so quiet, he scarcely snores. in the summer, the sea is calm and peaceful.

it shows many ways that the sea can be compared to a hungry dog.