The tidal wave symbolizes the confusion the dreamer has at this time of his life. Perhaps he is stressing out a lot about some matter. The dream suggests to do something immediately about it, because the stress is too hard to cope with. The tide wave is the symbol of your survival instincts either.
Dream dictionary: watch youtube time sitting dream meanings
The dream in which you are being in the class, but in reality you are already an adult, shows some memories that are very important to you from your childhood. If you are child, it is very normal dream because of the time you spend in the school.