In 1896 Magnus Volk wanted to extend his successful electric railway in Brighton, England. To advance it would have involved costly works to construct a steep climb to the top of the cliff or a viaduct running along unstable undercliff, so he created a railway which ran through the sea.
The “Daddy Long Legs” operated until 1901 on its 2¾ miles journey. This ‘sea voyage on rails’ was a mix of tramcar, pleasure yacht and end-of-a-seaside pier, all mounted on four 23ft-tall legs 100 yard offshore.
Classified as a seagoing vessel, it was subject to the maritime law of the period, which required it to be equipped with a lifeboat, lifebuoys and a qualified seagoing captain.
From here, and the BBC, via the retronaut