Often dreams of drowning stem from being overwhelmed by something or someone. This dream could be that you are concerned for some reason about one or both of your friends. I say one or both, because dreams can be hard to interpret. They may have been together because in their "waking moments" maybe they are always with each other. But maybe only one of them is having trouble. As for you seeing them later and them saying they were okay. My guess would be that maybe on the "outside" all seems fine, but maybe "internally" something is wrong. Have you attempted talking to them individually to see if they are okay?
I think having this dream that you are worried and needing to know if something is wrong. Maybe it's something deep that one or both of them feels they can't share... or maybe they are just having a "simple" trouble. Either way, couldn't hurt to ask if you are close to them. That's what friends do. Then maybe it will help you sleep and have better dreams at night.
That sounds to me like you want to finish something,but u are afraid of consequences. It prolly has nothing to do with your friends. Dreams are very useful. Its u telling yourself something you know you need to know ,It comes out coded,only u have the key.
Maybe you are just worried about them in general? I don't really believe that dreams mean anything.