Heads of state, mayors, scientists and policymakers have gathered in France to tackle what is being described as a global emergency facing the world's seas.

The U.N. Ocean Conference is opening in France as pressure mounts to turn promises into action on protecting the ocean.

While President Trump opted to skip the conference, his actions since returning to the White House in January overshadow almost every conversation among delegates and activists, in meeting rooms and halls erected around the old Port of Nice, with its yachts glimmering in the sun.