invention includes an annular shoulder 32 extending radially outward from the top end of the caisson 20 the bearing assembly 22 coaxially surrounds the upper portion of the caisson 20 just below the shoulder 32 the uppermost part of the bearing assembly 22 is a steel top bearing ring 34 disposed so that the bottom surface of the shoulder 32 rests on top of the top bearing ring 34 the lowermost part of the bearing assembly 22 is a steel bottom support ring 36 that is seated in the receptacle 24 in the bottom end of the hull 12 as described above arranged between the top bearing ring 34 and the bottom support ring 36 of the bearing assembly 22 is a plurality of flex elements comprising a plurality of steel flex rings 38 alternating with and separated by elastomeric flex rings 40 both the steel flex rings 38 and the elastomeric flex rings 40 are formed in a u201c dished u201d or arcuate configuration defined by a common radius of curvature as are the bottom surface of the top bearing ring 34 and the top surface of the bottom support ring 36 the steel rings 38 the elastomeric rings 40 the top bearing ring 34 and the bottom support ring 38 are bonded together by well known techniques the flex elements 38 40 are enclosed within an elastomeric outer sleeve 41 preferably about 1 2 cm in thickness that is fixed between the top bearing ring 34 and the bottom support ring 36 the configuration of one of the steel flex rings 38 is illustrated in fig5 which also shows the interior of the caisson 20 and the risers 30 passing through it the configuration of one of.