This so called moeder is impossible to kill without the strongest water dino. And it is even harder to escape the moeder because she can spawn electric eels and they will try to stunn your dinosaur and kill you and your dino
The Bloodstalker can pull a Moeder (just like it can with the Forest Titan). Have boats loaded with turrets waiting at the surface. Takes ages and Bloodstalker survivability its very low if unprotected. The hardest part is getting the Moeder to the surface.