How was a float-out lighthouse built onshore and placed at sea?

A float-out lighthouse is a specialized structure designed for locations with a suitable, leveled seabed. The construction process involves the following steps:

• Onshore Construction: The lighthouse, featuring a cylindrical tower atop a large concrete base (often 15 meters or 50 feet in diameter), is built within a shore berth.1
• Towing and Positioning: Once completed, the massive structure—weighing 4.5 million kg (5,000 tons) or more—is towed to its intended offshore location.1
• Sinking and Stabilization: The tower is sunk onto the prepared, leveled seabed. The base is then filled with sand, relying on the structure's immense weight for stability.1
• Telescopic Design: To improve stability during the towing process, the tower often consists of multiple telescopic sections. Once the base is firmly founded on the seabed, these sections are raised to their full height using hydraulic jacks.1

This innovative method of lighthouse construction was largely pioneered in Sweden.1