Three major effects of currents are-
1. Effect on Climate — The climate of the coasts becomes warm or cool according to the current washing the coast which may be warm or cool.
2. Effect on Marine life — Ocean currents move organic material off the coast which is the food of planktons. The more the planktons, higher the concentration of fish.
3. Effect on commerce — On account of influence of warm currents, harbours are kept open in winter, facilitating trade throughout the year.