I made one before out of all PVC fittings and pvc pipe and I drilled holes in the pvc pipes as well to allow water to get in so it would sink, but never got a chance to use it...
OK Gobber, AKA Ron PC is acting crazy. I made the trap just like a rabbit trap. Used a thin acrylic sheet from Lowes. ($11 and some change) Used superglue gel to take into place then used silicon to finish it. Rigged the door with a fishing line through a hole in the top and drilled a hole in the back to squirt or place food in. The fish go in after it and you simply pull the door shut using the string. Works good since the clear acrylic does not make them fell like they are actually going into anything.