Consider the following statements regarding ocean salinity and density:

1. The salinity of ocean water is highest at the equator due to intense evaporation.

2. An increase in salinity always leads to an increase in water density.

3. Deep ocean water has higher density than surface water due to lower temperatures and higher salinity.

4. Freshwater inflow from rivers increases ocean salinity near coastal areas.

How many of the statements given above are correct?