Question: Where are the majority of marine organisms found?
Disambiguated questions and answers: question: Where in the ocean are the majority of marine organisms found?
Where is the zone in the ocean that the majority of marine organisms are found?
answer: coastal habitats and coral reefs
Photic zone
photic zone, euphotic zone, epipelagic zone or sunlight (or sunlit) zone
Natural Questions answer: coastal habitats (from the Wikipedia article "Marine habitats")