there has been some mention of this in the forum before. the thing is the hardware already exists to do it. Vasa swim erg, concept 2 rowers, kayakpro output ANT+ and it can be read as a power meter by zwift easily. i just tried it today on the vasa erg since i got the new ant+ computer. i can only do 60 watts, so that limits my speed to about 15mph but it works. why not just create a little beta swim/row/paddle section in watopia, maybe by ocean blvd, or by the running bridge. create a swimming and rowing avatar and there you go. sure the demand is not huge right now, but people already own these machines, why not give it a shot?