Other thing is that there's evidence that women who have water births tend to tear less as the water really softens the area. I gave birth to my boy 3 days ago and despite having quite an ordeal in the pushing stage (I had to push without contractions as wasn't getting them close enough together to get him out) and despite the fact that I'm a horse rider and have a really strong pelvic floor which means I'm tighter and more likely to tear I managed to deliver him with only a couple of minor grazes, no tears whatsoever. I think that was due to the water birth, an utterly amazing midwife and probably some luck as well.
In all honesty though even without tearing by the time your baby arrives and is in you won't care less what's going on down below. I'm very swollen and was pretty uncomfortable for first day but every time in look at him I realise I'd do it all again a million times for him