Well I honestly believe that there's life on other planets somewhere in the galaxy. It's just impossible to assume that earth is the only planet that is perfectly poised between its sum and moon to support life. Moreover, earth wasn't always able to support life and it took may years of terraformimg to get to this point so who's to say there isn't another planet out there that doesn't have the same potential for life.
Secondly scientists make the assumption that carbon and water are required for any form of life to survive, but that may not be true. Other life forms could exist which have and require different things to survive. It's possible that silicon based organisms exist and it's also possible that there are elements which we don't know of which can serve as the building blocks of life that are present on another planet.
Humanity has only just begone to explore the galaxies and its way too soon to even assume that there isn't life elsewhere. Moreover I once watched a documentary on TV which alleged that the US government has seized over a dozen unmanned aircrafts of unknown origin. I don't know just how true that is but if it is them there's your answer already, life outside planet earth exists.
As far as subsea human life goes, I'm not sure about this one, but the thing is that the story of Atlantis exists and I firmly believe that there's some truth behind every folk lore or tale. They always stem from a truth of sorts and maybe the story of Atlantis is no different.
I have no definitive proof to support the existence of subsea Human life but seeing as all of the subsea ocean floor has not been explored then I can't say for sure that they don't exist.
I hope this helps.
@Alaisguineasis, In my opinion UFOs (May be higher Intelligence species) were their in times and in my opinion the ancient stone art and drawings on different Architectures and Structures are telling that there were species which were not from here, but there is no clarity but in my opinion if something is there and it's truth then truth will reveal itself. Stay blessed 🙂