What is the force that opposes the movement of an object through water?

Drag is the force that opposes the motion of a body through fluids including water

In air, you'd call it air resistance, pilots call it drag. In water, some call it

water resistance, or just plain drag.

Whatever it's called, it's the friction between the object and the fluid, plus

the force needed to push the fluid out of the way to let the object get through.