I started by finding lots of videos of sharks swimming online, observe its motion curve, and found that it is similar to the pendulum animation. So I animate the shark swimming in place, but it is not very natural, Then I continued to observe it,it looks much better after add head rotation. Then I designed the traveling route of the shark, which is the most satisfying part of the project for me and it makes the shark swimming look more flexibly. Finally, adjusting the direction and range of the shark’s body swings the animation is almost finished. I’m having some problems when importing animation files into Unreal Engine,the texture was miss! so I try found the solution on the Internet.then i export one fbx format file which save the model and texture, and export another file in alembic format which save the animation data, Then import them into Unreal Engine separately and the problem was solved.