We had pan-seared scallops last night (http://terrygruggen.blogspot.com/2011/05/pan-seared-scallops.html). They were spectacular because they were fresh...as in never frozen. They were shipped right from the sea to Byerly's with no chemical intervention by man.
Fresh scallops look like the photo above. Note that they are dry, which is precisely why they are referred to as "dry scallops". If you set them on a paper towel, they give off next-to-no liquid. When you cook them up, they are sweet. They taste like the ocean.
The scallops in the above photo are not fresh. They have been previously frozen. They are referred to as "wet scallops" and when you see them in the store they are often sitting in a white, creamy liquid. They have been treated with a preservative and whitening agent called sodium tripolyphosphate (STP). If you put them on a paper towel, they will give off a ton of liquid. STP increases the water retained by the scallop, often by as much as 30%. So frozen scallops end up being a poor value, compared to fresh, as you are paying for a lot of water.
Sodium tripolyphosphate gives the scallop an unpleasant chemical flavor. It's impossible to get rid of that taste. Your only choice is to mask it by pre-soaking the scallops in a mix of water, lemon juice and salt*. If you care about putting the best tasting and healthiest scallops in your mouth, buy only fresh. There is a world of difference and it will take you but a single bite to discover it.
*Mix 1 quart cold water, 1/4 cup lemon juice and 2 tablespoons salt and soak scallops for 30 minutes.