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.
An archaeologist studies artifacts and remains from past cultures.
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