Einstien is said to have gotten the inspiration for reletivity by imagining he was on a motorcycle.

Imagine a surfer. The wave he is riding is infinitly wide, 20 feet long, 100 feet high, perfectly straight, perfectly rigid, and and moving towards a perfectly straight, infinite shore at 4000 miles per second at an angle of one degree. The board he rides has zero friction with the wave and all is happening in a vacum. How fast does the surfer go?

Sine of one degree 0.0174524064 times speed of wave 4,000 miles per second equals surfer speed 229,194 miles per second.

Speed of light 197,000 miles per second.