Septic Swimming

This thread is inspired by Jimmy T's musings re 'garbage yardage' which incited some debate pro and con, but, of course, resolved nothing. I chose the thread heading, not to compete with Jim (who is a master wordsmith, albeit an epic hallucinator), but to allow posters to discuss any drill, set, exercise, common injury therapy, piece of equipment etc. that they feel will actually do damage to us. In other threads over the years, some of these opinions have been voiced, but I thought it might be useful to have a dedicated thread. Please have some grounds for your assertion, but you don't have to be a sports scientist either. Perhaps we could inspire some vigorous discussion? I'll start by mentioning a basic one (to me): I loathe kicking with a kickboard. I feel that it compresses my cervical vertibrae and could lead to neck problems (I have a pre-existing neck problem and any time I try using a board it gets aggravated). I also feel that the board doesn't allow you to assume a correct body position for kicking. Any takers? Feel free to state your own pet concern(s).