Creating a new D&D world, part 2

I recently purchased The Ultimate RPG Game Master's Worldbuilding Guide: Prompts and Activities to Create and Customize Your Own Game World by James D'Amato and it, and going whale watching, inspired me to create a new D&D world. So here we go! I'm going to use prompts from the book to begin crafting this world. These questions will pertain to the small island on which the adventure begins. 

You can read part 1 of my planning here.

These are the (ever so slightly modified) open-ended questions about magic on page 34. I will try and answer them all.

• What is a folk belief or superstition related to magic?
• That it is more ancient than the islands themselves
• What profession or institution depends on magic?
• Healers to some extent
• Those who send important or secret communications
• How has society developed differently because of magic?
• It gives additional hope
• What can these practitioners offer the world that others can't?
• Fast communication
• Amplified abilities
• Where might someone learn magic?
• Generally, it's done through an apprenticeship
• There are a few islands with schools, but not this one
• When would someone seek out a practitioner?
• Mostly when they are desperate
• But those who are very rich also seek them out for flashier entertainment
• The powerful also seek them out for security, espionage, etc.

(Prompt from The Ultimate RPG Game Master's Worldbuilding Guide: Prompts and Activities to Create and Customize Your Own Game World by James D'Amato)

"Humpback Whale (Megaptera novaeangliae)" by V.L.