Secchi is the mobile interface to the Secchi Disk project enabling any seafarer to take part in a global study of the phytoplankton in our oceans. By using this app you will help us learn more about the phytoplankton at a time when their habit is altering due to climate change. The phytoplankton in the sea, although they are invisible to the naked eye, are the ocean’s most important inhabitants since they begin the plankton food web that underpins the marine food chain. Today, there is evidence