There are features of this sequence that are very similar to dreams I used to have growing up.
The waterfall, I would say, probably represents emotional transportation, an exhilarating one. Water is a powerful element and it comes in all forms (lakes, rivers, oceans, water bottles...the way it moves and the type of body it holds is always significant). It's interesting that it was a source of playing for you at first, but then turned into something that these kids needed to be saved from. I'd pay attention to the other person who you were communicating with, and assess what type of regard/feelings serve as the foundation for your relationship with them. Is this a person who has the authority to require permission in general?
The goop is interesting - a bit ambiguous, but clearly, one should run away from it. It reminds me of games I used to play with older brothers, who wanted to get a rise from me, and put a little pep in my step. Do you know anyone who would enjoy psychologically chasing you and see it as a game?
The treasure chests being bloody makes them sound daunting, but perhaps more valuable, they contain truths that you may already know but are scared (or distracted) from looking at. Sometimes the truth sucks.
The people you should know, but don't feel close to possibly indicates that there are people in close proximity to you, but with whom you feel little to no intimacy or trust for. Maybe there is safety in numbers, but it lacks a sense of fulfillment.
I hope this helped!