Speleologist .
An Ecologist is a scientist who studies ecosystems.
A scientist who studies the earth and what it is made of are geologists
A geological scientist studies rock and stones.
Soil scientist
The study of earth is geology, so a geologist.
The name for someone who studies caves is a speleologist or a spelunker.
The name of a scientist that studies sports is called a sports scientist.
An arachnologist
A scientist who studies crystals is known as a Crystallographer.
A scientist who studies animals is called a zoologist.
A scientist who studies animal life is a zoologist. There is no particular name for a scientist that specialises in platypuses.
The name of the scientist that studies artifacts remains of cultures from the past is an archeologist.
Underwater Spelunking
The name for this type of scientist is a teuthologist
This answer is a entomologistA scientist who only studies fish is called an ichthyologist.
environmentalist
ecologist