Abstract: A Buoyancy-Controlled Lagrangian Camera Platform and method for use to observe layers of the open ocean. The platform has subsystems for recovery, for its camera, and for its buoyancy engine, which has a buoyancy engine and engine controller to control the platform depth. The engine controller adjusts the buoyancy engine volume with an adaptive PID control system and gain scheduling to control the buoyancy engine. The method for observation consists of a camera platform, a surface vessel with an echosounder, and a means of communication between the two. The vessel uses the echosounder to identify layers of the open water for the platform to target for observation. Instruction and feedback between the platform and vessel are communicated using an acoustic modem. The vessel also uses the acoustic link to track the Buoyancy-controlled Lagrangian Platform with repeated queries on its depth and range.