defined by the manmade islands of the preceding figures pilings not shown may extend inside the bookend elements 201 202 for achieving maximum structural integrity it will be appreciated that fig1 shows a cross section of an island and that a plurality of elements 201 202 may be used to define a perimeter of an island peninsula or the like fig1 b illustrates a bookend reformation 210 comprised by bookend elements 211 212 each secured by a piling 213 214 these differ slightly from the bookend elements 201 202 in that bookend elements 201 202 of fig1 a are provided with extensions 209 which lie under the fill 217 and or the sand 218 in fig1 b pilings 213 214 are simply extended upwardly into the elements 211 212 and downwardly into the floor 215 of a water body 216 to provide support for the elements 211 and 212 on the floor and to help define an island or a sandbar or perimeter for an existing or a manmade island fig1 illustrates a modification of the invention wherein a center support column is utilized to mount the formation structures as described above and is particularly useful where further support is needed for those structures accordingly fig1 illustrates a center support column formation 220 including a center support.