interior of each of the corrugations of one of the edges and are received in the same manner in the other interiors of the other corrugations of the other edge this will assure a rigid fit between the longitudinal edges 4 of the jacket 1 these plugs also help in locating the edges 4 relative to each other in a self aligning manner when the jacket is installed after all the assembly takes place in an underwater environment and the visibility might be hampered fig3 a shows a different seal 15 to be used between the edges 4 when they are closed this seal 15 is a rectangular seal but having openings 15 a therein to accommodate the plugs 12 there through when the plugs 12 enter the openings in the corrugations turning now to fig4 which shows a different fastening system for closing the jacket onto its edges 4 this fastening system consists of a buckle system 16 of the over center type to this end the buckle 16 includes two plates 17 and 19 which are riveted by rivets 17 a and 19 a respectively to the top or outside surfaces of the respective corrugations 3 plate 17 has.