AquaTek™ X1 Advanced USM - Universal Support Material is water-soluble
It works with a number of common 3D printing filaments to make complex parts turn out better, when used with the dual Extruder printers.
Though the price for a 500g spool may seem unusually high, the typical cost per part of support material is not necessarily a large cost.
Most parts can be printed with just a small "interface" layer of USM between the main plastic used for the part and the main bulk of support that can also be printed in the same material as the part. So the USM becomes only e.g. 10% of the total plastic being extruded.