How do snapping turtles catch their prey?

Box turtles, land tortoises, and any aquatic turtles have the ability to put their legs, arms, and head in side of their shell. The shell is the turtles protector/house if someone threw a turtle it would go into its shell and the shell would hopefully protect it from the hard ground. Most turtles the shell is Greenish, Grayish, or maybe other different colorful colors and those colors are usually the almost exact thing that is probably under water. Like seaweed, Rocks, other fish, and ect. so they stay by the objct so it is almost nearly impossible to see.