Ok so I did more brainstorming for my species:

-Live in Britain, mostly France and Germany.
-Can move extremely fast in water, but are slow on land.
-Carnivorous, mostly eats fish and small lizards/birds.
-Humans and bigger aquatic animals are their main enemies.
-Live in small groups, up to five animals live together, usually.
-Mostly flop around on land, can swim very well, is well adapted to big impact.
-Are currently closed to everyone except good friends. If you aren't sure, you can ask me.