CTD units are incredibly important to ocean research, measuring three basic factors of sea water — conductivity, temperature, and depth. Almost every major research vessel has one. But the units are part of what ensures that it’s expensive to get started doing ocean science. Each one can cost between $5000-$25,000. Now, a group of ocean scientists are trying to finance the design of an open-source CTD that could be built by anyone for less than $200. You can help fund their efforts at Rockethub.