Poll 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 and
fuel 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.