Ocean waters worldwide have received a "D" for health, but the outlook is actually better than scientists expected, says a new report.

Part of the third annual Ocean Health Index, the overall global score of 67 out of 100 for ocean health analyzed sustainability, measuring how well the ocean can continue to provide benefits such as oxygen and food, National Geographic reported.

Despite ranking in the "D" grading range, the score was not an unpleasant surprise.

"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," said Conservation International's Steve Katona, managing director of the Ocean Health Index, as quoted by 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," he said.

The researchers analyzed ecological, social, economic and political factors for each ocean region and then used a computer model to process the resulting data. The 2014 index scored the health of Antarctica and the Southern Ocean for the first time along with the 15 other ocean regions that are outside of national jurisdiction.

"The high seas do a lot of good for people," said Katona. "They regulate climate, generate oxygen, provide food, and contribute to a sense of place."

The overall score for this year is an improvement from the 2012 score of 60 as well as the 2013 score of 65. American waters received a score of 72 in the latest index, an increase from 63 in 2012, while China scored 65, rising 10 points compared with the 2012 index.

Katona contributed the rising scores to conservation efforts including marine protected areas and a more precise way of measuring the effects of fisheries.

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