least two of said piles having platform receiving guide means at their upper ends the platform includes a plurality of legs for fixing to corresponding ones of the piles with at least two of the legs being hollow and being provided with respective plungers slideably mounted therein for co operating with said platform receiving guide means each plunger is associated with a releasable fastening capable of holding the plunger fixed in its leg and of releasing it suddenly on command to drop into engagement with said platform receiving guide means the releasable fastenings of at least two of the plungers are arranged to release simultaneously on a common command application_number US 29053781 A description in fig1 a a platform 1 is carried by a transport barge 2 a support structure for receiving the platform is fixed to the bed of the sea 3 the structure has piles whose tops project above the surface of the water one such pile referenced 4 is shown in the figures at its upper end there is a platform receiving guide means in the form of a female cone 5 the platform 1 has a leg 6 corresponding to each pile for example a platform might have four legs to be made fast with four piles at least two of the legs 6 are constituted by hollow cylinders that are closed at their upper ends by a bar or stop 7 the leg shown in the figures is of this hollow type a plunger.