On their latest report card, the world's oceans were docked points for overfishing, pollution, climate change, and weak environmental protections, ultimately earning a D grade.

The Ocean Health Index is an annual report issued by the environmental group Conservation International, and though it assigns a grade to the world's seas, the implication is that humans have performed poorly when it comes to protecting and conserving one of Earth's most valuable resources.

Some ocean advocates suggested global decision makers deserved a failing grade.

"I think many people are surprised that the score is that good, because people hear all the bad news about overfishing, pollution, death of coral reefs, climate change, and so on," Steve Katona, managing director of the Ocean Health Index, told National Geographic. "If you come home with a paper from school, your parents aren't real happy if it's a 67, but most people expected a score for the ocean that was worse."

To amalgamate the grade, a team of researchers -- including scientists from the University of California, Santa Barbara, the University of British Columbia and elsewhere -- scored ocean health, region by region, using ecological, social, economic, and political factors. A top score of 100 doesn't necessarily mean an ocean is the picture of pristine health, only that it will continue to sustainably offer the food and oxygen that make it so vital to human life -- not that any perfect scores were warranted.

The report card offered scores for different oceans, regions and countries. The latest index is the first time Antarctica and the high seas have been included. And though the Southern Ocean is relatively healthy, the coastline of Antarctica remains technically unprotected and fishing and illegal whaling activities there continue to encroach on vulnerable species like bluefin tuna, basking sharks, minke whales and Gentoo penguins.

The healthiest overall ocean, according to the index, is the Western Indian Ocean and East Central Atlantic Ocean, with scores of 79. On the other end, the Northwestern Pacific Ocean scored the lowest of any other oceanic region, with a score of 53.

Researchers with Conservation International hope the report card can encourage nations to incorporate important ocean conservation and protection policies. China is one of the countries that did just that after their oceans scored a paltry 53 on 2012's report card. This year, China got a 65.