Aqualungs
Before the invention of aqualungs, there was no guarantee that you’d be able to spend more than a couple of minutes underwater. But when this ingenious invention came out, people were spending lots of time scouring the ocean bed and getting a first-hand look at all sorts of beautiful sea crits.
A few decades later, we have aqualungs that can hold onto more oxygen, allowing deep-sea divers to spend more than 30 minutes fully submerged and several hundred feet below the surface. Inspiration for this device came when René Commeinhes created the first breathing apparatus for firefighters. Ironically, the same system to help people fight fires would help others breathe underwater.