Humanity has long known that fish swim due to undulating body movements, but there was no consensus about the essence of this hydrodynamic process. The two working theories and controversies over them lasted for more than half a century, until recently Tingyu Ming from the Beijing Center for Computational Science took up the task of simulating the process on a supercomputer. It turned out that both models are right, but it all depends on the fish itself.
Two virtual models were created, one with a fully movable body of independent segments, in the form of an eel, the second only with a large moving tail, like a mackerel. Using real-life fish-watching data, Min's team calibrated their models, calculating the force, torque and power generated by each one. And she got different results, but with the same conclusion - both options are successfully used to develop high speeds under water.
As it turned out, everything very much depends on the anatomy of a particular underwater creature. Mackerel has long, elastic tendons that run along the entire spine and allow energy to be stored and transmitted to the propulsion mechanism at the base of the tail. But if each vertebra in the spine behaved independently, like an eel, this principle would not work - and vice versa. This means that nature and evolution have created very different principles of underwater movement, and there is no point in looking for a middle ground.
For engineers, this is an annoying limitation and at the same time an incentive to further creative research. It is not difficult to reproduce the movements of an eel or mackerel, models of robotic fish already exist. But building large machines suitable for payload in the same way is still a task.