This Policy Brief supports all marine practitioners, those who devise and apply policy and those affected by the policies, who need to show that the seas should remain healthy. This must be both for nature, by supporting the ecological structure and functioning, and for humans who can continue obtaining goods and benefits from the seas. It gives existing and new approaches and methods which focus on healthy oceans. It furthermore emphasises how practitioners should define natural and societal health and focus on the metrics available for determining whether or not management reaches these as a goal.