So I’m trying to make sure I understand exactly where you’re stuck. At that part there are two sides to the water. From the left side you can’t progress. You need to get to the other side to do something (there’s a hint as to what you need to do once on that side, and a way to get to that side that doesn’t involve the water room). Then another person can go to the left side and use what you did to get across. Hope that makes sense. If not, I will explain further!