Hydrologist
Ornithologist
An entomologist.
Marine biologist.
A person who studies the formations and changes of glaciers, is a glacier geologist.
H2o
A language expert is commonly referred to as a linguist. Linguists study the structure and usage of language, including grammar, syntax, semantics, and phonetics.
The Mediterranean Sea is a proper noun, the name of a specific body of water. A proper noun is always capitalized.
Juan Valdez is the name of a coffee expert.
The compound noun Red Sea is a proper noun, the name of a specific body of water. A proper noun is always capitalized.
The proper name for a water snail is an aquatic snail.
The name of a colon expert is a gastroenterologist.
The proper name for a rainbow is an "optical phenomenon" caused by the reflection, refraction, and dispersion of light in water droplets resulting in a spectrum of colors forming in the sky.