Most use diving license, but no other major licenses are needed.
Marine biology
You need a degree in Marine Biology
because we need to know what is in the sea
Sometimes only if you need to know how the animal died.
No, you don't need a special insurance or licenses to open a bed and breakfast. You can read about how to start one at www.fabjob.com/BedAndBreakfast.asp
A degree in biology would suffice, but degrees are offered in marine biology which would allow for a better chance of a job in the field.
No, but then you would be a marine biologist who understood nothing about physics.
Yes, you need special marine salt.
motherfvcker
They do need a Nascar license in order to drive a stockcar or truck.
It all depends on where you are working, like in an office or out in the ocean. If you are working in the ocean that you will need a SCUBA health insurance.
The oceans are earths last great frontier. Less than 20% has been explored and most of that not very well. Marine biologists will be in great demand in the future.