Nowadays, air amplifier is used as a blower or sucker in different branches of industry. With the advent of some compressed air into this device, air pressure greatly decreases and its velocity increases, leading to suction of a great volume of air (up to 20 times of the volume of the consumed air) into the device and under the influence of the Coanda effect exits from the other side. If this device can function similarly in water, it could be used as a marine thruster system with many advantages. Among the most important of these advantages are as fallow: it only needs a pump not a power plant to drive the marine system. There would be much flexibility in the placement of the pump in the marine vehicle. Moreover Power Transmission between the power plant and the propulsion system and also the problem of sealing of the Power Transmission shaft will be omitted. It is expected that this new propulsion system to produce much lower noise. It also would need much less maintenance effort. On top of these advantages is the enhanced manoeuvrability of the marine system. Finally, it has no rotating vane; therefore hazard of collision with external objects reduces. In this research, application of this device as a marine thruster was studied. To accomplish this, effect of a few parameters on its performance was investigated experimentally. The independent variables in conducting this investigation include the size of gap and rate of water flow into it. The dependent variable is the thrusting force developed by the device. The experiment was conducted for 9 different gap intervals and five different flow rates. Subsequently, in the second phase of the project, a numerical model of the air amplifier was developed and its performance in water was simulated using the Fluent software. Afterwards, the results obtained from the numerical modeling were compared with those of the experimental data. A rather close agreement was observed between them. It was concluded that numerical modeling of such systems can be done accurately and results obtained from such simulation may be considered as reliable. The findings of this study demonstrated that the air amplifier performs to a great extent similarly in water and air. The flow rate sucked in can be as great as 145 times the flow rate pumped in to the device. The results show that there is an optimum gap for the device at which its thrust per unit consumed energy is a maximum. Moreover, the optimum thrust force per unit consumed power for this device was 0.15 Newton per watt which is comparable with those of propellers (i.e. 0.15 to 0.2). This demonstrates that this device can compete with other thrusting systems. Key words: Air amplifier? thrust force? numerical? experimental, water, noise