Why is raw fish sometime soaked in milk to make it taste less fishy?

The fishy smell of fish is due to the chemical trimethylamine or TMA. This chemical is hydrophobic, or in other Words, is attracted to fats. The fats in milk therefore attract this fishy chemical (solubilizes it) helping remove it from the fish along with the oils. This is why fish known to be more oily are commonly soaked in milk as well.