The Energy Endeavour, jack-up type drilling unit under tight tow to stand off position at new location Halfdan Charlie in the Danish sector of the North Sea. The rig personnel jack down the legs to pin spudcans - to seabed. Then, the tugs run anchors to enable the Tow Master to maneuver the unit into final position alongside the unmanned satelite platform - when the spudcans are over the desired foot print, the legs are jacked down once again to make contact with the seabed and raise the hull out of the water until they have +/- 3 meter air gap. The rig is then loaded up with pre-load ( seawater ) pumped into tanks - this weights up the legs evenly to establish if the spudcans / footings are stable with minimal penetration. When the OIM / Tow Master are satisfied that all is well - the pre-load is dumped and the hull structure is jacked up to final elevation. To enable a rig to be move from one location to another the weather conditions have to be favourable, minimal sea swell and wind - over a period we call a weather window. Rig moving is regarded as a "High Risk" operation - many units have been lost because of changing weather conditions or failing to remain water tight throughout the voyage. As you can see from the picture the legs are extended to maximum height to reduce drag through the water but this also makes the unit more susceptible to listing and possible turn over. See title link for disasters over the years. Before & After shot below is the Adriatic IV jack-up and the Temsah ( TheTamshee ) gas platform off the Egyptain coast in August 2004 
