If mine weren't broken I would be honored
I can tell you that it would have no problems penetrating. I was able to punch right through 1/4'' plywood from 15'' so it has power. The bigger ones have even more. You just have to get the feel of your speargun if/when you buy one. It is not the same as firing a firearm, you have to shoot it a different way. Mine was given to me when I was 10 (I have a cool aunt and uncle in FL) but I never used it till I was 16. I have no idea what model or who makes it but it is VERY similar to the one with the yellow handled photo I posted.
They are also a hell of a lot of fun to shoot, a lot more than a pistol crossbow! Those things break too easy, the strings come unwound and NO one makes good arrows or quarrels for them. You can get great speargun tips in different sizes and types from all over online and the shafts are MUCH better quality.
I think the one in the movie is this one...
P.S. I go by Olaf