the boaters in your venue and see what they want. Every venue is a bit different. The San Blas veggie boats are a big deal for cruisers, because they deliver a lot of produce that is just not available elsewhere in the San Blas and/or its a bit of a trek to get otherwise.
The USVI probably has different needs.
For each product or service figure out how to make it profitable. The San Blas veggie boats charge a premium, but we are very happy to pay it. Its a big deal when they come thru...cruisers announce their arrival on VHF
. Sure is convenient to privsion with them tied up right along side...no treking to wherever and humping bags around...well worth the higher cost.
Another boat there will deliver diesel/gas and the cruisers coordinate bulk fuel
deliveries to keep the cost down.
In the San Blas many cruisers give water to the locals because many cruisers have water makers/catchment systems. Watermakers are becoming more common cruising gear
so that market is shrinking. Beer
may thus become the more profitable liquid deliveries.
I used to sail in another venue in which a local pizza shop would deliver within a certain radius. You just called in your order on VHF and good hot pizza would arrive. Very popular. In New England
its common to find boats selling lobster rolls. So food
is another common product. Maybe work out a deal with local restaurants and provisioning
companies to deliver their products. Cruisers could choose from a menu and you charge a fee to deliver, plus maybe work out a commission with the provider.