A tourist?
An Aquatic Nomad
a naturist
Prank like a joke! A Crank call is made for the purpose of annoying, upsetting, or threatening someone.
Someone who travels in search of new lands, tribes, or cultures is often referred to as an "explorer." Explorers venture into uncharted territories to discover and document their findings. In a broader sense, they may also be called "adventurers" or "voyagers," depending on the context of their travels.
Light travels in straight lines that we call rays.
A call out is an incidence of someone being summoned for a purpose, or a meeting or rally held to find participants, for example for a sports team or a specific activity.
An astronaut.
A vessel that travels underwater is termed a submarine.
When you think of the author's purpose, think PIE. Persuasion, inform, entertain. The author's purpose in Call It Courage was to entertain. He also showed that wars are horrible, messy, and unkind. We need to do what we can to prevent future wars.
passenger
medium?
rays.