Newhall is a newly terraformed planet with large oceans. Stands to reason that water is the planet's primary commodity. Newhall's people live on small island chains or on floating stations on the oceans.
Newhall's water plants are always in need of workers, hence the Alliance's generous incentives for settlers who move here. Terraforming new worlds requires a lot of fresh water, and Newhall has water to spare. Processing the water and preparing it for shipping isn't an unproblematic job, though. The water needs to be collected, desalinated, purified, packaged, then loaded for transport.
Those of Newhall who don't want to work the water plants can make a good living fishing. And there's always the tourist centers, for those who like to swim and cavort - or those who want to tend to those who do.