Since the cathodic protection systems were first applied, engineers were aiming to optimize their design based on experience and intensive monitoring. The experience has shown that the most effective and the most cost-effective way of preventing corrosion of the underwater ship hulls is combination ICCP system and protection coatings. The correct position and current of the anodes is a subject of vital importance to the performance of the ICCP system as a whole, especially for ships that sail through the different environmental conditions such as those in Venice lagoon. In Venice lagoon we meet fresh, brackish and salt water whose electrical conductivity influence the effectiveness of the cathodic protection. The aim of this paper is to get a picture of the effectiveness of the ICCP system with mutual dependence on three parameters: salinity, hydrodynamic conditions and the number and position of the anode. An additional objective was to examine the possibility of using a single anode, which has not been the conventional approach. For this purpose, the ship was made of low carbon steel on which is applied two-component epoxy coating and anti-fouling coating. To test the effectiveness of the ICCP system we induced damage to the insulation. MMO anodes have been installed at two positions: on the sides of the ship closer to the stern and under the boat. Tests were performed in 0.0%, 0.2% and 3.2% solution of NaCl, and with and without hydrodynamic conditions. Cathodic protection is carried out with potentiostatic method, therefore by maintaining a constant protection potential equal to -0.05 V vs. Zn-sea water reference electrode. The results show that with the increase in salinity distribution of potential gets more uniform and better because the increase in conductivity of the electrolyte increases the range of protection which then increases the effectiveness of the ICCP system. An unconventional approach, to the use of the ICCP system with one anode has given equally good results (distribution of potential) as well as ICCP system with two anodes, because it managed to polarize all defects in the insulation to the potentials within the interval protection. The introduction of hydrodynamic conditions caused potential shifts in the anodic direction, but this did not influence much on corrosion protection level. Output voltage of rectifier units for ICCP system with one anode was higher than for the ICCP system with two anodes. By introducing hydrodynamic conditions the output voltage and output current increased in both cases. For ICCP system with one anode and at hydrodynamic conditions it will be required higher power of transformer-rectifier units.