FRP over foam
In other words, built like a surfboard. FRP = Fiber Reinforced Plastic, so fiberglass, carbon fiber etc.
They can sculpt it in a foam of their choice, then coat it with FRP: that means painting 2-part epoxy* polyester or polyurethane on it, lay down fiberglass matting, more poly/epoxy/equiv, layer on layer. Finish up with thick primer/paint or a gelcoat.
Or, they may be creating a mold and assembling in the reverse order like a production catamaran: gelcoat first (the surface of the mold defines the final surface), then the FRP, then the foam.
They don't necessarily last for years since they have staff ready to repaint anything. But if you are seeing a finish that is tougher than ANYTHING you can do with any hardware store product, then you are looking at marine grade stuff, which is all 2-part material. It's awesome, but it will also maim you if you disrespect it. That's why Home Depot won't sell it to you lol.
The "B" part is typically either BPA or some form of diisocyanate. You need a moon suit to spray the stuff. But once the epoxy-style cure happens, the nasty stuff is entirely consumed in the reaction, and is gone (provided you don't use way too much B-part).
They do let you play with 2-part epoxy garage paint, because that is a) applied with brush or roller per instructions, and b) consumers usually mix the entire sold product, so no risk of mixing errors, and c) they don't paint garage floors very often. The stuff is mostly harmless when handled that way. The toxin is in the resin which does not evaporate, so just keep it off your skin and you're all good (and really skin is a pretty good barrier for occasional exposure).
* similar to epoxy in the sense that it's a 2-part chemical you mix and then it self-cures after a certain time, without need to interact with air or moisture... except an alternate chemical that works the same way, such as polyurethane. Due to epoxy's vulnerability to UV light.
