​Horseshoe SOS is a comprehensive guide to everything you ever wanted to know about horseshoe crabs, including: anatomy, conservation efforts and the controversy surrounding use of their copper rich (blue) blood. There is also an FAQ to answer all of your most pressing horseshoe crab questions. The app also allows you to easily report tagged horseshoe crabs (or separated tags) to the US Fish and Wildlife Service simply by opening the app and choosing the Report Tag button on the navigation screen.