Locks do not work that way, at least not unless you want to use them to go below sea level.

Locks always have to be fed from reservoirs on the upper side of the lock and each lock cycle transports one lock full of water to the lower side of the lock. This is the reason locks are so energy efficient, because we do not need to do the lifting ourselves, we just let the water do it.

There are some lock designs that store part of the lock's content in some side-reservoir to use e.g. the upper half of the water to refill the lower half on the next cycle but that is about as much as can be done to conserve water without installing huge pumps that would require a lot of energy.