False on two counts. In a perfect vacuum, light is merely tied for first place as the fastest thing in the universe—and in water, it is surprisingly easy to outrun.
The "c" in Einstein's is famously known as the speed of light—approximately 300,000 kilometers per second—but it is more accurately described as the speed of causality. According to special relativity, any particle with zero mass must travel at exactly through a vacuum. Light is made of massless photons, so it hits this limit. But so do gluons, the particles that bind quarks together inside protons and neutrons. Gravitational waves—ripples in the fabric of spacetime itself—also travel at exactly . If the sun were to suddenly vanish, the Earth would continue orbiting a ghost star for eight minutes and twenty seconds, experiencing the loss of gravity at the exact moment the sky went dark.
The more surprising exception happens when light is not in a vacuum. When photons pass through a medium like glass or water, they interact with the material's electromagnetic fields, slowing them down. In water, light drops to a relatively sluggish 225,000 kilometers per second.
This creates a loophole. High-energy particles ejected from nuclear reactions can easily exceed 225,000 kilometers per second. When an electron shoots through a pool of water faster than light can travel through that same water, it creates an optical sonic boom called Cherenkov radiation. Just as a supersonic jet pushes air aside to create a shockwave heard as a boom, a particle outstripping light in a medium creates an electromagnetic shockwave visible as a bright blue glow. This is why the water surrounding the core of an active nuclear reactor glows blue—the subatomic particles inside it are literally traveling faster than the light around them.