Good grief, that many files!

From what I know after a little checking is that the Particles.dsd file is from the Depthcharge shake mod, the Particles.dat, dated 12/2007 is a total mystery, I actually thought it might have been from one of your early SH4 effects mod, but went through them all & differ, this one is 465,748 bytes.

The Val files are from Rubini's wake fix, Shells.sim is dated 2006, so not likely to be that. I went back in and reloaded the game but the effect and damage is gone, the U-boat is the 7c.
Edit: Could this happen using GWX 2.1 U-boats & 1.03 Particles.dat