Animal-borne data loggers (ADL) recording triaxial acceleration, angular momentum and magnetic strength have been increasingly used over the past 20 years to study the movements of animals. ADLs have allowed researchers to estimate field metabolic rates and kinematic measurements like tail beat frequency and have increased our knowledge of the movement of animals in the wild. However, these tools only provide insight into an animal’s movement via a single location on the body. This limits ADLs use for whole body kinematic studies. Our aim was to develop a datalogger from opensource, off-the-shelf components to measure movements at multiple points along an animal, and thus allow for 3D reconstruction of midline kinematics during unrestrained swimming. This new datalogger is designed around a microcontroller (feather adalogger) to record measurements to an SD card from multiple MPU9250 inertial measurement units (IMU) placed along the midline of a fish. The readings from each sensor can be fused together to provide a 3D orientation of each location on the body. We have tested this data logger in a computer-controlled flapper in a laboratory flow tank to generate known undulatory kinematics while simultaneously recording high speed video to provide ground truth measurements of body motion. In controlled lab settings, the data logger was able to accurately reflect the timing, direction, and magnitude of movement of multiple locations along the body. This new tag has the potential to allow for whole body 3D kinematic measurements from fish in the field, and a better understanding of the diversity of fish locomotor behaviors.