This unit spans three to four weeks and connects the topics of density, pressure and buoyant force to the hands on activity of designing and operating under water craft. Students will explore and calculate pressure changes and buoyant force underwater through a series of short experiments. Using the knowledge gained in these labs, students will build a model of the Trieste, the first bathyscaphe to reach the bottom of the Mariana Trench. The model illustrates Archimedes’ Principle and that adding weight greater than the displaced water will cause the object to sink. They will then construct a working model of a remote operated vehicle (ROV) based on the successful “Seaperch” design from MIT. As a culminating activity students will design their own blueprint for a submersible. An extension of this engineering activity using a set of water sensors that can possibly be deployed underwater with the ROV is also explored. Using the ROV with sensors attached to collect data such as dissolved oxygen in a local marine or aquatic environment can be done as an extension or final product if equipment is available. Students can then develop a hypothesis around how these variables are connected and design an investigation of the health of the environment.