a sentence:)

[Jenny Lau]

Our boat anchored in the dark as oversized swells crashed upon its hull.
What does "as oversized swells crashed upon its hull" mean?
Dose "swells"meas big weaves here?Thank you !

The following is the context:
It was one of those black nights at sea. No shade of gray separated the water from the sky, nor was there a peek of light from a distant shore. Our boat anchored in the dark as oversized swells crashed upon its hull. A huge 16-mm underwater motion-picture camera was lowered over the side to a photographer in the water. The photographer signaled that the camera was secure, and the rest of us plunged into the water, each person carrying a large underwater light tethered to the generator of our boat.

[Tdol]

A 'swell' is the up and down movement of the open sea, so it is like a wave.

[Jenny Lau]

Thank u ,tdol!
I'm sorry, these few days I got a cold and haven't been on net. Sorry for my delay of reply and thank u again

[Tdol]

Hope you're better now, Jenny.