I believe this is fixed in ProjectExtended 1.1.0 for MC 1.15.2. If you run into it again, feel free to let me know and I will re-open it. (Not releasing a fix for 1.14.4 as I do not have time to maintain multiple versions of MC at once with how much of my free time has been going into working on Mekanism). I am also not positive it is actually fixed, but I updated some code to match a chance vanilla did in 1.15 for the path that the trident returns along and at the very least it seems a lot smoother/less glitchy. So for this reason I believe it is fixed

Originally posted by @pupnewfster in #2 (comment)

I just loaded up the 1.16.5 v1.2.0 of Project Extended and this problem exists again. I had great fun playing with the trident until I actually took it underwater. The first time I threw it, it never came back. Seems to have disappeared. I can't find it anywhere.

Im having this issue, anytime its thrown into water it disappears.