There is a flexible, bendable type of pipe that is commonly used inside of the aquarium on the water return lines. The most common brand name is Loc-Line. It is used to direct and control the water flow to specific areas of the tank.
It has fittings that will connect with standard pipe sizes. The rest of the pipe snaps together to make custom size lengths, flow controls, etc. It can be taken apart and put back together again and again.
It can wear down after many years of use so be careful using it outside of the tank.