Read the passage carefully and answer the following questions:

Protecting the health of coastal waters is now a matter of national policy in many countries including the United States of America. World leaders are beginning to prescribe a revolutionary remedy that conservationists have been promoting for years: marine planning and zoning. The idea is a natural extension of management policies that have guided the cities and landscapes for nearly a century. Zoning advocates envisioning a mosaic of regional map in which every watery space on the planet is designated for a particular purpose. Drilling and mining would be allowed only in certain parts of the ocean; fishing in others. The most critically threatened areas would be virtually off-limits. Whereas people can easily find maps telling them what they can do where on land, the marine realm is a hodgepodge of rules emanating from an army of agencies, each one managing a single use of symptom.

Why protecting the health of the oceans is necessary?

for our co-existence 

The correct answer is Option 3: for our co-existence

While the passage emphasizes the importance of protecting coastal waters and mentions resource use and trade routes, it does not specifically state that those are the reasons for protection. The phrase "protecting the health of coastal waters" implies a broader perspective on sustainability and co-existence with the marine ecosystem.