The Seychelles has floated a plan to deepen its marine conservation efforts in return for a groundbreaking sovereign debt deal backed by funds including the Leonardo DiCaprio Foundation.

The actor and environmentalist is one of five investors working with The Nature Conservancy to undertake the first ever "debt for nature" swap to protect the oceans.

In return for the pioneering $20m debt relief plan, the island nation this week brought into force hotly contested controls on its tourism and fishing industries to help reverse the damage to its coral reefs and marine biodiversity.

The plan rules out fishing in areas of high marine biodiversity, such as the Aldabra region, and limits fishing in other areas with "medium protection status", which have been used by commercial fisherman and tour operators for decades.

The debt restructuring will effectively funnel a stream of Seychelles repayments into a seperate trust, which will begin investing in schemes to build an environmentally sustainable "blue economy" from April this year.