The class Crustacea comprises the majority of the marine species of the arthropods, although there are many freshwater species and even a few terrestrial ones such as the common sowbug. The most familiar are shrimps, crabs, and lobsters, but the diversity of the crustaceans in form and biology ranges from the gigantic king crab of the Pacific Ocean to a myriad of planktonic forms comprising the dominant herbivores of the ocean.
Shrimp.
A marine crustacean that is like a shrimp and in the order Euphausiacea is called krill. Krill are found in each of the oceans on Earth.
Krill
Mantis
A copepod is a small crustacean that belongs to the group of zooplankton. They are an important component of the marine food web, serving as food for many fish and other marine animals. Copepods play a key role in marine ecosystems by cycling nutrients and energy.
Shrimp may be your answer.
The likely word here is the shelled marine crustacean, spelled "barnacle".
they eat small sea life.
Crabs, and the clawlike appendages are called chilipeds.
A lobster is a marine crustacean and the word 'internal' would not apply to them - your question can not be answered.
Prawns, or shrimp, are a type of marine crustacean, which are animals.
The crustacean is a goose barnacle.