Where there is enough water and food to sustain them. That means everywhere (including the Arctic and Antarctica) but deserts.
I assume you mean what part of the world. The answer to that question is that puffer fish live all over the world, from pacific to south Atlantic to freshwater rivers and lakes.
in the water under rocks and behind plankton
the part where water is
they live world wide
There are many fish in the sea...
Saltwater fish live in the saltwater seas and oceans around the world.
their gills
Grenadiers, better known as rattail fish, live deep in the arctic and Antarctic ocean waters. These fish were part of the most abundant in deep-sea fish families.
Butterfly fish are from all over the world and live in the coral reefs.
worldwide
the deep or the benthic zone
According to a million bajillion books i read, starfish live in every ocean around the world and can be commonly foun in tide pools and coral reefs. :)