By looking at the wake of a boat it helps you understand how sonic booms occur.
If you toss a pebble in a pond, little waves will form in concentric circles and move away from the point of impact. If a boat travels through the pond at 5 to 8 kilometers per hour, little waves will move away in the same way both ahead of and behind the boat, and the boat will travel through them.
If a boat travels faster than the waves can move through the water, then the waves "can't get out of the way" of the boat fast enough, and they form a wake. …
