Dakuwaga lives in the warm ocean, while Thelma Lake Monster lives in the cold freshwater lake. The former is a shape-shifting creature that can change from fish to human, and the latter is a large snake that likes to eat human flesh and fish flesh. Let
If they were crammed into lukewarm, brackish water, you'd have to be as brainy as a Billywig to imagine that Dakuwaga would be slaughtered instantly.' - Rolf Scamander
Talking about the accident at the opening ceremony of the 2014 Quidditch World Cup book club: