Yes, travel insurance is worth carrying for a trip to Independence, the mainland town most visitors pass through on their way to the Placencia peninsula by ferry across the lagoon. The honest reason to carry cover here is access and evacuation logistics rather than any particular danger in the town itself - Independence functions as a transit point, and what happens if something goes wrong nearby depends on getting back across the water and onward from there.
Independence has only basic local medical services, and anything serious typically means transfer first to Belize City, the country's main hospital hub, with international evacuation to the United States sometimes needed for complex cases. Confirm your policy covers medical evacuation and international repatriation explicitly, since that multi-step journey - not treatment in Independence itself - is the part most likely to involve real cost and delay.
The ferry crossing to Placencia is a routine part of most itineraries through Independence, and while it is generally reliable, rough weather or mechanical issues can disrupt the schedule with little warning; check that your policy covers transport delay connected to ferry disruption specifically, not just outright flight cancellation. Diving and other water activities popular around Placencia are worth checking for separately if they feature on your trip, since some policies cap or exclude them.
Hurricane season, roughly June through November, is the defining seasonal risk for this part of Belize, bringing the possibility of disrupted ferries, flights, and short-notice evacuation orders during an active storm. Trip-delay and cancellation cover matter more during this window than at any other point in the year.
Keep any clinic paperwork, ferry-cancellation notices, and receipts for emergency transport or unplanned accommodation if a crossing or evacuation is disrupted. Many policies require prompt notice before major expenses like evacuation are incurred, so check the claims process in your policy wording before you travel.