SLS materials can be treated with a sealant to fill small pores, thus making your part airtight and watertight. Of course, the final tightness will dependent on the initial level of pores, and the pressure of the water. This option is called ‘Sealing, standard’ in the Finishing dropdown when you upload your 3D file.
TuskXC2700T and TuskXC2700W, however, are water-resistant by nature. Both materials are suitable for strong, water-resistant prototypes with ABS- and PBT-like specifications (e.g. parts for water flow analysis and wind tunnel testing).
Metals on general are watertight, depending on the application.