Floodgate and Lock chamber

Floodgate noun - Regulator consisting of a valve or gate that controls the rate of water flow through a sluice.

Lock chamber and floodgate are semantically related in sluice topic. In some cases you can use "Lock chamber" instead a noun "Floodgate".

Lock chamber noun - Enclosure consisting of a section of canal that can be closed to control the water level; used to raise or lower vessels that pass through it.

Floodgate and lock chamber are semantically related in sluice topic. You can use "Floodgate" instead a noun phrase "Lock chamber".