This nudibranch feeds on a particular type of hyroid and is therefore rare to be seen in a seagrass bed. Shortly after this photo was taken the animal released itself from the seagrass and floated free in the water for a few minutes, perhaps trying to drift to a better feeding area.
The Rainbow Warrior is in the Mediterranean for a three-month ship tour taking action on the threats to the sea and calling for a network of large-scale marine reserves to protect the health and productivity of the Mediterranean Sea.