Why? Fish are called "free travelers"?

Living in the ocean? Fish has a slender body and an oval sucker on its head, which looks like a seal, hence the name. Don't underestimate this "seal". What is this? Fish can travel easily and eat for free. Whenever sharks, turtles or some big fish swim nearby, the fish stick to it with suction cups, adsorb on the big marine animals and swim around, while the big animals fill their stomachs with the residue of preying on their prey. Because? There are meat folds in the sucker of fish. When other large marine animals are attached, the water in the meat folds is squeezed out, which generates suction under the pressure of seawater, so the adsorption force is strong and it will not be easily separated. In this way, it can "travel for free" with big fish or ships. When encountering a sea area with a lot of plankton, it will automatically disembark and have a full meal. If there is no new "boat" to tie it, it will stick to the reef and "rest" and wait, so it is called "free traveler".