Water-based shipping is extremely efficient. (However, they should be forced to install pollution controls on their internal combustion engines instead of just injecting raw exhaust into the ocean.)

Of course, reducing their carbon footprint would also be good, but it's currently only 3% of global emissions:

https://yaleclimateconnections.org/2021/08/maritime-shipping...

The carbon impact of the stuff on the ships is likely much higher. For instance, this BBC article breaks it down for food, and, for ocean-shipped stuff, the carbon emissions of transporting the food is rounding error:

https://www.bbc.com/future/article/20220429-the-climate-bene...

The only real exceptions to the rule involve highly-perishable food that has to be flown in next day, but that doesn't have anything to do with ocean transport.

As far as I can tell, carbon offsets are a complete scam (vs. putting the money directly into stuff that reduces carbon production).

If anyone knows how to pay an existing company to extract carbon from the atmosphere, and store it in a biologically inactive form for > 1000 years, then I'd love to hear about it.