I'll keep these guys damp next time, and see if I can get a live shot. I found them on the frozen surface of a vernal pool in the woods.

Hi Tom. Great catch and great series of photographs. Your new lens is quite useful to reveal a lot more details.
As the genus name suggests, this species is connected with water. And requires a high air humidity to survive. That explains why they died so easily during transport. Next time make sure to add some moist piece of paper in your transport container.
Thanks to your new lens we can now see a lot more characteristics. Such as: this is a male specimen. Note the oval genital plate at the terminal segments (just behind the base of the furca). This species also has sexual dimorphism (quite rare in entomobryomorph Collembola): note the thickening of the outer side of the 2nd antennal segments, typical for male specimens of this species.
This species is adapted to live on the water surface: note the hypognath head (with mouth opening directed downwards to the watersurface), typical for watersurfacefilm dwellers (see also Podura aquatica). Note also the broad dentes which prevent pearcing the watersurfacefilm when the specimen needs to jump.