Woodifer - you sound like me, GBS was found in a urine sample early in 2nd pg so MW told me no HB (had lovely one with DS), no waterbirth, continual monitoring... all my 'bad' buzzwords, I left the surgery in tears. But as part of my research I rang the MLU, told them the situation and asked if I could deliver there instead of hospital and the lovely MW on the phone said they'd be happy for me to give birth there but that they couldn't give me the ABx so I might as well stay at home if thats what I wanted. I was so happy and Then she explained to me that the reason I would need to deliver in hospital if I wanted to have the ABx was because of the risk of complications from the ABx themselves, and her explanation that it was a huge dose for a tiny newborn, and carried a risk of deafness. So I had my ABx free home waterbirth despite a positive swab at 36wks, and did the same again for DS2.
I decided that I had most likely been GBS+ during 1st pg, and blissfully ignorant, and NHS guidelines say if you have had 1 confirmed GBS delivery and baby was healthy then they don't recommend the ABx for subsequent deliveries, so I crossed my fingers for DD, MW insisted I was discussed at their community team meeting so all the team knew the 'risks' if they were on call when DD arrived but none of them had a problem, and in the event it was the senior MW on the team who was on call when I rang and she couldn't see why my community MEW had made such an issue of it!
So in answer to Oiesha's original question - you won't show 'symptoms' during pregnancy because GB strep is just a bacteria that lives in your gut normally. A waterbirth is definitely possible, and although she had never seen any evidence or study into it, my last MW thought a waterbirth ought logically to be safer for a GBS baby as they get 'rinsed' on their way out!
Sorry, that ended up a bit longer than I intended, hope all goes well for you