that engages the threads 34 a 34 b between the running tool 30 and sealing element 32 disengages the corresponding threads 32 a 24 b between the sealing element 32 and the riser disconnect 24 the drill string 14 in fig1 may then be withdrawn from the riser 18 with the running tool 30 and sealing element 32 attached at the bottom end thereto and normal drilling operations may resume in water depths of several thousand feet or more it is therefore only necessary to remove the length of riser 18 to a depth just below that to which storm effects descend as an example only the topmost 500 feet of riser is expected to be withdrawn to the platform 10 in fig1 leaving the entire lower portion of the riser self suspended by enough buoyancy to avoid collapse thereof such procedure is expected to take only a few hours as contrasted with the several days it may take to withdraw the entire riser from the water the embodiment explained above with reference to fig2 in which the riser is displaced by pumping gas therein is only one method for displacement in other embodiments suitable u201c swab u201d devices may be affixed to the lower end of the drill string such.