The Pacific Ocean Neutrino Experiment (P-ONE) is a new initiative to construct one of the world’s largest neutrino detectors in the deep Pacific Ocean off the coast of British Columbia, Canada. Located in the Cascadia Basin region, P-ONE builds on a number of key strengths within the Canadian oceanographic community. The Cascadia Basin monitoring site is part of the NEPTUNE observatory of Ocean Networks Canada (ONC), which provides power and data connections to various deep ocean sites, accessible to experiments. In cooperation with ONC, the collaboration successfully deployed two pathfinder experiments, the STRAW projects, in 2018 and 2020, respectively. These pathfinder mooring lines aim to measure the optical and ambient background characteristics of the Cascadia Basin in a depth of 2660m. The P-ONE prototype line is the successor of these mooring lines and the next step towards the P-ONE neutrino observatory. The main objective of the prototype line lies in the construction, deployment, and operation of a complete P-ONE mooring line as a proof of concept of the individual components. This line will comprise of P-ONE digital optical modules to measure the emerging Cherenkov radiation by neutrino-induced processes and P-ONE calibration devices to provide in-situ calibration of the detector. The prototype line will be complemented by external geometry calibration units to verify the envisioned calibration principles.