There is a very important thing called 'drag' that happens when things move through the air or water. It's like getting slowed down by a really strong wind or a lot of water pushing against you. So things that move through air or water need to figure out how to deal with this 'drag' so they don't slow down too much and can go really fast.
The 'drag crisis' is when something that's moving through the air or water suddenly goes from having a lot of drag to having very little drag. It's like if you were being slowed down a lot by wind and then suddenly the wind stops and you can go really fast. This can happen because of different things, like if the angle that you're moving changes, or if the air or water moving around you changes in some way.
When something experiences the 'drag crisis,' it can be good or bad depending on what it's trying to do. For example, if an airplane suddenly has less drag, it can go faster, which is good if you're trying to get somewhere quickly. But if a swimmer suddenly has less drag, they might sink, which is not good at all! So people who build things like airplanes and boats and race cars need to be very careful to think about drag and how to deal with the 'drag crisis' to make sure they are safe and work well.