> That's a lot of barges.

Maybe bring another Evergreen ship there and move containers onto it...?

20,000 TEU, not containers.

TEU being Twenty-foot Equivalent Unit, and containers generally are either 20ft or 40ft long.

You can see from pictures that most of the containers are 40 foot ones. Also, the ship doesn't appear to be at full capacity to me. See https://imgur.com/a/b8neNkR (top is as full a picture as I could find, bottom is current). My guess is ~6000 40 foot containers in its current state.

What's the difference, for purposes of estimating workload?

Containers are 1 or 2 TEUs, although doubles are more common for long distance, so you're probably looking at 10,000-ish containers.