Posted: 11/02/2014 at 23:22
Callitriche is common in fresh water in the UK, and from my botany books the appearance is similar for a couple of species. I'm not totally convinced, however.
Stansty, why not post your photos on iSpot? They are great at ID over there. www.ispotnature.org
Edd, you are right, there are lots of alien plants (love that expression, makes me think of plants in spacesuits!)