Seawater velocity (m/s) :  1500.0
 Depth(mbsf)  Depth(mbrf)   1wtt(s)   tt_correct(s)
   526.569  3326.069  2.158195  2.163815
   574.608  3374.108  2.182665  2.188292
   640.676  3440.176  2.226130  2.231765