Ulva

Photo: Ulva intestinalis.
Photo: Ulva intestinalis 0.

Algae in the shallows. Säppi, Finland. Wild. 2000-08-16.
Photo: Ulva intestinalis 1.
Photo: Ulva intestinalis 1.

Algae in the shallows. Tammisaari archipelago, Finland. Wild. 2004-08-01.
Photo: Ulva intestinalis 2.
Photo: Ulva intestinalis 2.

You can see why it's gut weed: it's just tubes, filled with air. Tammisaari archipelago, Finland. Wild. 2004-08-01.