Coasts and marine life around Britain are under pressure from pollution, coastal erosion, overfishing and climate change, experts have warned.
The Environment Agency says coasts are under pressure
The Environment Agency says better management of the seas and coasts could help protect their fragile ecosystems.
The recommendations are published in the agency's first State of the Marine Environment report.
Sir John Harman, agency chairman, said there needs to be a balance between using the coasts and protecting them.
The report found many coastal waters are at risk from pollution from fertilisers and pesticides.
These can change the delicate balance of marine ecosystems, which in some cases are already having to adapt as sea temperatures begin to rise.
It says the basking shark is an example of this, being one of several species moving north as the climate changes.
Authors of the report also say that there is an increasing strain on the coastline from human population, with around 17m people currently living within 10km of the England and Wales coast.
Sir John said British coasts and seas are "under pressure".
"Fish stocks are decreasing. Sea levels are rising and flood risk is increasing.
"The climate is warming up and marine ecosystems are changing in response.
"To meet these challenges we need to strike a much better balance between the different uses of our coasts and seas to protect the marine environment," he said.
"While we have seen improvements ... our challenges are changing and much remains to be done."
The Environment Agency has also said it supports the Government's commitment to create a Marine Bill to replace the current piecemeal approach to management of the seas and coast.