Flame, Highflyer taught me how to use a conibar 330 trap. He was trapping Otters at the time on his lake. The otters I have seen(not at my place) were not large. A Huge one I have never seen, but huge Beavers, yep seen and caught one with the trap. The large splash u describe sounds more like beaver. I think they look similar when in the water. Also lots of trapping info vids on U Tube. I have been expecting otters to show up but so far Zero Otters. Good luck, PS, we were not able to shoot the beav even after many attempts.