Concussion 
To dream that you have a concussion implies that you are wasting your natural skills and talents. You should take some initiative instead of expecting things to occur on their own.
Water Skiing
To dream of water skiing is a suggestion to learn how to trust yourself. The freedom that one feels while water skiing is something you are just beginning to experience in your waking life. You may have recently found peace in your spirituality.
Flying Machine
To dream of seeing a flying machine suggests that you will move forward successfully with the ambitions and goals you have set forth.
To dream about a flying machine that doesn't work indicates that the things you are fretting over, or worrying about, will fail to alleviate your concerns.