Assuming this is referring to Crescent Beach: Crescent Beach used to be a normal sandy beach area much closer to Lakeshore Drive when the lake level was higher. As the water level dropped the area is now more of a reedbed than a beach.

That area of the lake is still named Crescent Beach even though it isn't really a proper beach anymore. 

Sandy Beach and Long Beach were also differently shaped when the lake level was higher. They both have sand brought in from other sources to maintain them as the lake level has changed so they are partially man_made.

Source: I've been visiting White Bear Lake for over 20 years. Used Bing images for placement