"The orange spot on both of the individuals on the final image is an Acanthocephalan (Pomphorhynchus laevis) that uses Gammarus spp. as an intermediate host. Cool observation!"

Evidently this is also responsible for the striking blue colouration of the second individual.

Moved from Scuds.

These are Gammarus, certainly G. lacustris, the only species of the genus in Alberta. Very common in most lentic habitats in the province.

Moved from Amphipods.

These little freshwater Gammarid crustaceans are commonly known as scuds (sometimes "backswimmers" or "sideswimmers" for their erratic, topsy-turvy swimming motions). Although common in many freshwater environs, they often achieve extremely dense populations in alkaline, limestone-influenced watersheds. They scavenge in detritus and aquatic vegetation, and trout in cool limestone streams often feed extensively on them.

I wish that I could tell you more about the ID of your specimens, but I can only guess that they might be Gammarus.

I believe these are amphipods--they look just like the "sandhoppers" you see on beaches. We have a section for them, but it appears that no one here knows much about identifying them.