Trailing weighted nets across the seabed wrecks fish stocks and kills carbon-capturing seagrasses—but one fisherman’s sculpture project has turned the tide.

A 1970s plan to grow underwater limestone objects has been repurposed as a way of regenerating the seabed, reestablishing corals, and stopping coastal erosion.

Ocean exploration to prepare for deep-sea mining has been greenlit in Norway. These are the startups hoping to benefit.