A subsea system for intervention or deployment comprising a spool (9, 109) adapted for mounting subsea, a carrier (4, 4, 5′, 34, 104) adapted for suspension from a surface vessel or platform, a guide line (8, 108) wound on the spool, the free end of the guide line connected to the carrier and means (11) for driving the spool in one direction to pay out a length of guide line as the distance between the spool and the carrier is increased and in the other direction to reel in the length of guide line as the distance between the spool and the carrier decreases.