Jumbo shrimp should boil for seven to eight minutes and large shrimp for five to seven minutes, while medium shrimp only need three to four minutes to cook through completely. The boiling times for crab legs range from three to eight minutes, depending on their size and type.
Snow crab legs are far smaller than king crab legs. Snow crab legs only require three to four minutes of boiling time. King crab legs boil for twice as long, or six to eight minutes, as they have thicker shells and meat. Most store-bought crab legs are already cooked before they are frozen. Frozen crab legs must be thawed completely before adding them to salted, boiling water.