If an animal has a set of organs held together and protected by surrounding fluid, the animal is a
acoelomate
pseudocoelomate
coelomate

The answer is coelomate.

Coelomates are animals which body cavity (coelom) is filled with fluid. Fluid surrounds organs, protects them and allows their free movement and growth. All vertebrates are coelomates.

Pseudocoelomates have pseudocoelom partly filled with fluid. So, fluid surrounds organs, but not as tightly as in coelomates. The example for pseudocoelomates is a roundworm.
Acoelomates have no coelom. The example is a flatworm.