In a bid to combat carbon emissions from large vessels, designers have introduced Project 821, hailed as the world's first hydrogen fuel cell superyacht. Developed by Danish shipyard cooperative Feadship after five years of meticulous design and construction, this zero-diesel yacht stands nearly 400 feet long and operates using emissionless hydrogen power. The innovative hydrogen cells convert lightweight liquid hydrogen into electricity stored in lithium-ion batteries, emitting only water vapor instead of harmful pollutants. Designed by British studio RWD, the vessel harnesses hydrogen to power both its propulsion system and onboard facilities, reflecting recent advancements in incorporating this green alternative across various modes of transportation. However, storing liquid hydrogen at -423.4 degrees Fahrenheit within massive cryogenic tanks poses significant spatial challenges, as it requires 8-10 times more storage space compared to diesel fuel. Despite this hurdle, the superyacht boasts luxurious amenities spread across five decks above water and two below, featuring a range of facilities from pools and jacuzzis to gyms and living spaces. While the vessel currently faces limitations in storing sufficient power for extended voyages, it can operate silently at anchor for a week or briefly navigate emission-free at 10 knots in specific marine zones. Additionally, an advanced energy management system optimizes power consumption onboard, supporting the use of MTU generators on HVO biofuel as an alternative power source. Feadship's 'Project 821' not only represents a leap towards sustainable luxury yachting but also sets a precedent for future developments in fuel cell technology and eco-friendly maritime solutions.