Vanishing Depth Charges?

So I noticed last night while on my first real career patrol that as I watched in free cam the Depth Charges dissappeared after what seemed to pass about 20 or 30 m. Does anybody else have this?? I did hear explosions and saw them on the surface but I did not see them underwater. Ive never had this happen before and am just wondering if this is a small glitch in the game now or if I enabled a mod that conflicted it?? Im going to test this out soon to see if it was just my graphics card goofing or Im really having vanishing DCs.