This video shows two crests colliding with each other. This is called constructive interference. When the two crests collide for he moment, they combine to create one bigger wave
this video demonstrates destructive interference where a crest collides with a traugh. When they collide they cancel each other out.
in this last video, we attempted to create a standing wave. In the video you can see the nodes where the destructive interference occurs, and also the crests and traughs where you can see the current nsttuctove interference.