Has this ever happened to anyone and what would you call it?  This morning, I was sitting outside remembering and thinking about last nights dream, when I all of a sudden was brought back to a dream from I don't know when, but I remembered that old dream very clear.  What triggered this old dream was the water that was in my dream.  I was thinking it was the same body of water, just a different part of it.

I've had this happen before. I've also had repeating dreams happen before. Sometimes a dream or nightmare will repeat itself until a problem that is inside the dream or mentioned within it that is representative of something in your actual life is resolved. For me, I have had recurring nightmares about various phobias of mine that happened over and over again until I faced that very same phobia. Once I conquered the phobia, nightmares about it stopped completely. It doesn't have to be a phobia necessarily but an unresolved problem that is manifesting itself in your life over and over again and once you face it, the looping dream will stop. Another thing that helps for me, is after I have a dream and wake up, especially something reoccurring, I will say out loud with my voice, "what does this mean?" Sometimes it is answered with a series of thoughts. Sometimes this happens almost immediately, sometimes it may take a few hours of even a day, but I don't remember a time where I asked and got no answer or answer fragment. Hope this helps.
Peace,
David.