▁Japan ▁Self - Def ense ▁Forces ▁hel ic op ters ▁next ▁day . ▁The ▁ship ▁was ▁rep a ired ▁at ▁a ▁dock ▁in ▁Sh ing ū , ▁W ak ay ama ▁and ▁returned ▁to ▁service ▁in ▁June ▁ 2 0 1 1 . ▁ ▁World ▁record ▁According ▁to ▁the ▁IO DP , ▁on ▁ 2 7 ▁April ▁ 2 0 1 2 , ▁Ch ik y ū ▁d ril led ▁to ▁a ▁depth ▁of ▁ 7 , 7 4 0 ▁meters ▁( 2 5 , 4 0 0 ▁feet ) ▁below ▁sea ▁level , ▁setting ▁a ▁new ▁world ▁record ▁for ▁deep - se a ▁dr illing . ▁This ▁record ▁has ▁since ▁been ▁sur pass ed ▁by ▁the ▁ill - f ated ▁Deep water ▁Hor izon ▁mobile ▁off sh ore ▁dr illing ▁unit , ▁operating ▁on ▁the ▁T iber ▁prospect ▁in ▁the ▁Mississippi ▁C any on ▁Field , ▁United ▁States ▁G ulf ▁of ▁Mexico , ▁when ▁it ▁achieved ▁a ▁world ▁record ▁for ▁total ▁length ▁for ▁a ▁vertical ▁dr illing ▁string ▁of ▁ 1 0 , 0 6 2 ▁m ▁( 3 3 , 0 1 1   ft ). ▁The ▁previous ▁record ▁was ▁held ▁by ▁the ▁U . S . ▁vessel ▁Gl om ar ▁Ch allen ger , ▁which ▁in ▁ 1 9 7 8 ▁d ril led ▁to ▁ 7 , 0 4 9 . 5 ▁meters ▁( 2 3 , 1 3 0 ▁feet ) ▁below ▁sea ▁level ▁in ▁the ▁Mar iana ▁T rench . ▁On ▁ 6 ▁September ▁ 2 0