Hydrodynamics is the the action of fluids in motion. Objects move much slower in water compared to above water. This is because water is about 800 times more dense than air, 55 times the amount of viscousity. This makes a huge difference because it requires 55 times the amount of force to make it go the same distance at the same speed. There are many other important factors in hydrodynamics such as drag, lift and thrust. Drag is the resistance of a force pushing underwater. Lift is caused directly by suction. If something is curved upward, the water will flow faster over the top than under the bottom, therefore causing the object to go down. Finally, thrust is the action of when a force is pushed backwards, causing the object to go forwards.