Question

If the density of the water is equal to the density of ship then does it sink or float?

Answer 1

If an object is exactly the same density as the liquid, it will not move up or down. It will just stay right where it is (unless it is pushed around by water currents). If you put it on the surface, it will remain on the surface . If you push it under the water, it will stay under the water, without moving up or down. It's not so easy to achieve neutral buoyancy exactly.
Fish and submarines do it by having an internal container that they can pump air and water into or out of in order to change their density.