So, water is feminine, which would usually take 'sa' as the third person possessive. Am I correct that 'son' is used due to the starting vowel? And is that true for all feminine nouns starting with a vowel, and with 'ma' and 'ta' as well?
Yes, the feminine possessive pronouns (ma, ta, sa) are replaced with masculine ones (mon, ton, son) when the noun starts with a vowel.
It really is a shame that duolingo is such a great app but the speech sounds nothing like a REAL French person. I guess thats why its free!
How do I see the responses to my queations without having to open this or any specific exercise?
As soon as you post a comment/ question, you automatically start following that discussion. After that whenever anyone comments on that discussion, you get an email about it. This is a default in Duo. You probably have an email now and already have the answer to your question :)
je parle le français et je vous assure que la pronociation était si dégueulasse que j'ai entendu fais son eau au lieu de c'est son eau. de plus la phrase ne veut pas dire grand chose.