I had 2 water births - I was lucky. I was well prepared via daisy birthing classes for all the eventualities, in particular I was walking around or on birthing ball with tens machine until I got to 5/6 cm then got in pool- you ideally need the baby head pressing on your cervix to keep things going. (Learnt that at class) water obviously takes some if the weight off hence in theory can slow things down as less pressure on cervix. By being well informed I felt I was much more in control and understood the potential risks/benefits of the available drug options and various positions to both me and baby.
I tried gas and air and hated it, made me sick - So I dumped that lol.
Under water I felt really safe and cocooned - and private. Forgot water was see through 
Midwife was great, I had DH there but to be honest he didn’t have much to do at all - someone to chat to between contractions I guess? I wouldn’t have minded being on my own - everyone is different though so do what feels right for you (but don’t worry about being alone as they will look after you).
Good luck whatever happens - I had pretty nasty tears to be honest but still have overwhelmingly great memories of both births, and the key I think for me was being well informed of what happens so I understood it. I chose to have natural placenta delivery for instance and no vit K - because I read up on it ahead, I knew about all the millions of old wives tales on bringing on overdue labour, that sort of thing. Really enjoyed reading Ina May Gaskin (American midwife with loads if birth stories) - as to be honest before this I had no idea what to expect, if they did cover the full details in biology class I clearly glazed over 😂)
Good luck whatever happens, and to be honest the best advise is to remember it’s just one event - how they come into this world feels like such a big deal at the time, but it really is just one tiny snapshot of your (and their) life together. So long as you all go home safe and on one piece (ish) then you have had a successful day. Same with feeding - everyone has an opinion but do what’s right for you at the time
Good luck! 