Prelude's maiden voyage Far off the coast of Western Australia, deep beneath the ocean, lies a remote reserve of natural gas. But reaching it has been considered too challenging. Until now. So Shell has embarked on what it calls the prelude project. Instead of piping gas to land, Shell will liquefy natural gas at sea. And here at the Samsung shipyard in South Korea, the vision is becoming a reality. As the idea turned to steel. The journey begins, because we're going to build the floating LNG facility. The steel turned to blocks.... Think of it as lego. Lots of these blocks being put together. It's huge. And the blocks turned into the hull.. The success of this project is in our hands at the end of the day. Now the team is preparing for its greatest test yet. It's time to launch the biggest hull ever sent to sea. Willie Gray is getting ready to make history. In less than 24 hours his team will float a hull measuring, nearly half a kilometre long and weighing more than 200,000 tonnes. It's a moment that's been years in the planning. But they will have just two hours to make it happen. So we have from about 7 am to 8:45, is the tidal window. So it's quite short actually. And if we don't achieve it then the next one is in the evening and that's in total darkness and we have to wait until the following morning again. So everything is geared up to meet that key timing on Saturday morning. During that time, the hull will be navigated across the harbour, where the next stage of construction awaits. So it's a great day and of course for any Scotsman, it's St Andrews day, so we absolutely have to meet that target. And getting to this target has been a remarkable achievement. In May this dry dock was nearly empty. Less than 8 months later sits the largest hull ever built. It's a fantastic sight, it really is. For Huw Jones it means the task of fitting the liquefaction modules can now begin. Each year these modules will produce enough natural gas to meet the needs of a city larger than Hong Kong. There are 14 different modules all doing different things. Each module weighs on average about 5, 5 and a half thousand tones. So right here in front of you today, there's about a quarter of it sitting on this quayside. Inside the dry dock, the engineers are making one last inspection. Because once launched it will be 25 years before Prelude will return. Here we are standing in the moonpool area. This is where we introduce the gas and liquids so they can be processed on the topsides. Tomorrow morning the structure must be floated off these support blocks, then navigated safely out of the dry dock. There is no margin for error. This draft, 80 centimetres. Its not very much, its tight, but we're in good hands. Laughs. No one's nervous, we're in good hands. SHI are experts at this. This is what they do. As temperatures dip to zero, the launch team gets ready to start. At 9:15 right on schedule the vast valves to the dry dock open. And Willie Gray is watching closely. Well it's now 20 to 11 at night and we commenced filling the dock actually at 915. There are 60 persons on board who have been positioned in strategic locations. It's a precautionary measure We're expecting to commence floating sometime around 1 to 1:30 tomorrow morning. And at 7 o'clock, when it becomes first light, we should commence to tow out from the dock.. In the early hours of the morning Prelude starts to float. By day break, the hull is standing tall. Morning Mr An, how are you? No wind? Conditions for launch are near perfect. The weather's just above freezing. It's just getting to first light. It's going to be a brilliant day and everybody is looking forward to the big event. The tug boats jostle into position, 9 are needed for the short journey across the harbour.. And with that sound Prelude, slips out of the dry dock. It's amazing, it's very big it's very impressive and it's a fantastic achievement for everybody It's really fantastic, amazing, unbelievable. We made it. Yeh, we are very proud of it. And we can say it in French.... Fantastique. It's a special moment for the Prelude team and there to witness is a crowd of nearly 500 people. We've got all the families of Shell and of Technip here as well. They've all come to Korea, you know it's a big step for them to be working here too. And for them to be part of this great event is absolutely fantastic, it's great to have them. Can you forget this? Will you forget this? It's absolutely fantastic, unbelievable. By the time we put our modules on, it's going to be higher than that accommodation block the whole length. They're clear. After 18 million hours of design and development. Including 14 months in construction. Prelude slides gracefully across the water. For Willie Gray there's time for a snap shot for the family album. And a pat on the back from the boss. Well done mate I'm really proud of you. Today they can celebrate. But tomorrow it's back to work. Because once moored a whole new phase of the project is about to begin.