Looks like they're toothed belts, so they should perform OK when wet.
It also looks like they have a belt per wheel, so there's a good deal of redundancy. Because there's apparently no differential gearing it means you have to lift up the outside wheels in tight (e.g. walking speed) turns, but that often happens naturally anyway on a skateboard.
It also looks like they have a belt per wheel, so there's a good deal of redundancy. Because there's apparently no differential gearing it means you have to lift up the outside wheels in tight (e.g. walking speed) turns, but that often happens naturally anyway on a skateboard.