As part of WBUR's "Boston Underwater" series, we go to the water's edge in Boston: Belle Isle Marsh. The marsh is a stop along the T's Blue Line, which features a mile-long tunnel that travels underwater, and connects the North Shore with Boston's downtown.

 But as sea levels rise along Boston's coast, the marsh is the last thing standing between the ocean and maybe the end of the Blue Line as we know it. And it serves as a bellwether to future climate-related issues in Boston.

We speak with WBUR reporter Simón Ríos and Julie Wormser, Deputy Director at the Mystic River Watershed Association.