This is a whistle stop tour around the oceans. We used to think they were huge and inexhaustible. Huge they are, covering more than 2/3 of the surface of our 'blue planet'. But inexhaustible?

• Look at the highlights in this section to realise that this is not so.

• Luckily, there are still beautiful stretches of oceans left. But see how 'shifting baseline' (particularly in our own perceptions) is playing tricks on how we get used to destruction faster than it's happening.

• Explore what you can do to help stop the plunder and destruction.

• Team up with others near and far – together we can achieve more, have fun and learn something as well.

Each category gives you a few highlights so that you get a sense why leaning back and relaxing might not be a good idea. You will discover additional background materials by clicking on the links as we add information. Our sections publications, links and reviews provide you with additional resources to dig deeper into the issues and explore what the big picture is, but also what it may mean in your local context.

The sections exhibitions and projects show what we have already done or are doing at the moment.

The section 'What to do' proposes things you can do, including links to support-worthy campaigns, petitions and activities, and of course, participate in specific Mundus maris activities. Individually, we will not be able to ensure sustainable behaviour, but collectively, we can do much, not the least by participating in ordinary political processes to ensure good rules and their effective enforcement. It's not too late and many others are already active to save our seas and restore them to a healthy state. Add your voice and action.