Grab fireworks from caravan town after getting the blueprint and set them up in two ways. Launch them by hand underwater or through objects, detonate on impact. Mount them on surfaces for automatic skyward launches, use paintbrush to customize colors from basic white

For combat, fireworks only hurt seagulls, not a great choice against bigger threats like screechers or sharks. Worth noting, if you place multiple fireworks, you can time them for cool synchronized displays

Good to know, crafting needs 5 planks, 10 plastic, and 1 explosive powder. Maybe interesting that launching 50 of these gets you the real fireworks achievement which is a nice bonus while playing around with displays

Put them anywhere on the raft that makes sense, experiment with timing and colors for the best show. Just remember they're more about style than fighting, so save your resources if you're looking for weapons