Why isn't it safe to drink ocean water?

In my oponion, you cannot drink salt water because of its salinity(how much salt is in it) and the Mercury from the fish can also get in the water. There is also much pollution with sewage and what not. You can however obtain fresh water from salt water through the process of desalination. This is when pieces of ice berg's (most icebergs are made of fresh water) and they put in a special chamber that melts it and collect the water vapor.