The technology relates to a submersible water lifting assembly and automatic fire fighting system for unmanned platforms having said system (1) that is efficient yet simple to install, energy saving, noise free and economical. The submersible water lifting assembly can comprise a High flow Ratio ejector Pump (30/30A) that utilizes under water arrangements of unmanned platform and enables the fire-fighting system to efficiently lift water from the sea water; using the force of existing water injection system; eliminating the requirement of diesel engine driven pump, for lifting the water. It avoids fire risk of the safety system itself, even in conditions of a large fire, unlike that of the prior art.