Why Dunkirk needed both little ships and destroyers

Which ships were best equipped for the Dunkirk evacuation?

The operation needed the actual mixed force employed: little ships for shallow water, larger vessels at the mole, and destroyers for lift, protection, and gunfire.

The evacuation already used the right mix: small boats reached shallow water while larger ships embarked hundreds from the harbor mole. Destroyers supplied carrying capacity, escort, and direct-fire deterrence. Their guns also made bringing German armor close to the coast a much less attractive proposition. The force mix solved different access and protection problems at the same time instead of asking one vessel type to do every job.