Jök­ulsá á Breiða­merk­ur­sandi, the biggest river on the sands, though very short, only about 1,500 m. Comes from a 248 m deep lake, or lagoon, Jök­ulsárlón, the deepest lake in Iceland, at the foot of the glacier.

There are usually icebergs floating on the lake.

The river, which used to seriously hinder travel, was bridged 1966–67, but the bridge is now in danger due to the encroachment of the sea.

Boat trips are available.