A submersible pump (or sub pump, electricsubmersible pump (ESP)) is a device which has a hermetically sealed motor close-coupled to the pumpbody. The whole assembly is submerged in the fluid to be pumped. … Submersible pumps push fluid to the surface as opposed to jet pumps having to pull fluids.

A submersible pump pushes water to the surface by converting rotary energy into kinetic energy into pressure energy. This is done by the water being pulled into thepump: first in the intake, where the rotation of the impeller pushes the water through the diffuser. From there, it goes to the surface.