My Nightmare what does it mean?

Alright i know i already asked a question about a dream but it wasn't a nightmare this one was so the dream im in an abandoned house and i go upstairs to the attic and i had this dream ALL the time when i was like 7-8 and i would go up to the attic and there would be a broken floorboard and once i would step on it i would fall into water and there would be sharks in there and there was only one way out which was a hole in the bottom of the tank only big enough for me not the sharks and once i ped that floorboard and i didn't fall into the water i had this dream again but this time at the end of the attic was a light i don't know what it means at all