There are several types:
The name of the scientist that studies artifacts remains of cultures from the past is an archeologist.
Marine biologist. Actually, a Marine Biologist is someone who studies marine organisms (plants, oceans, and animals), but someone who studies MAINLY marine mammals is a marine mammalogist.
An archaeologist(the study of the past by studying artifacts)
The name for someone who studies caves is a speleologist or a spelunker.
An archaeologist is the scientist who discovers and studies ancient artifacts. They use various methods to excavate, analyze, and interpret these artifacts to learn about past human societies and cultures.
A scientist who studies water (H2O) would be a hydrologist or a water chemist.
The name of a scientist that studies sports is called a sports scientist.
A scientist who studies floods is called a hydrologist. Hydrologists study the distribution, movement, and properties of water on Earth.
An arachnologist
A virologist is a scientist who studies viruses.
A scientist who studies animals is called a zoologist.
A scientist who studies radioactivity is called a nuclear physicist or a radiologist.
A scientist who studies animal life is a zoologist. There is no particular name for a scientist that specialises in platypuses.
Hydrologist
The name for this type of scientist is a teuthologist
This answer is a entomologistA scientist who only studies fish is called an ichthyologist.
Parasitologist