A moment of sheer wonder near the end of Rob Stewart’s final film pictures the conservationist lingering face-to-face with a gigantic, curious hammerhead shark against the white-sand floor of a shallow bay.

Like so many other vividly shot scenes of his communion with the creatures here, it’s intensely moving. His 2017 diving death hangs over almost every moment, but it also gives the film a weight and urgency that ensures its place as a legacy to his work. With the same signature energy of his 2006 Sharkwater, the affable activist travels to dangerous places to track the accelerating demise of shark populations—flying drones over mob-owned fin-harvesting docks in Costa Rica, diving into night waters to secretly film creatures caught in gill nets, and toting hidden cameras into the frozen holds of fishing boats stacked with tens of thousands of sharks in Cabo Verde. “My parents worry about me all the time, yeah. I just have this belief that I’m gonna be okay,” he says in one haunting voice-over. Besides offering fascinating underwater footage, the film acts as an ode to that fearlessness—but also to the wonder and curiosity that drove his vision.