The structure opposite Rue de Galet, which was dismantled by Occupying forces to build the nearby fortification, is normally hidden under about four to five feet of sand.
Tony Pike, press officer for the Channel Islands Occupation Society, said that the slipway was very rarely seen.
He said: ‘I do not know the age of the slipway – it was probably built in the 18th century – but you can certainly see the outline of where it was. Between around 1942 to 1943, the Germans would have blocked it off to construct a type 631 anti-tank bunker with a Skoda 4.7 cm PaK 36(t) gun.
‘There are other examples of the Germans doing this – the slipway at Bel Royal had to be cleared after the Occupation where another bunker had been built but this one was of fortress standard – with walls about two metres-thick.’
Mr Pike added that the recent storms had also revealed a section of the bunker and that granite blocks used in its construction were now visible.
He said: ‘There is usually about five to six feet of sand on top of it, it is very unusual to be able to see the toe at the front of the bunker.
‘Given how much sand has washed away from that area, I would not be surprised if people start finding ordnance left over from when the Germans did live firing practice. I would urge anyone if they do find anything not to touch it and to tell the bomb disposal officer, Stuart Elliot, or the States police.’