the spool frame 30 thus the sledge 12 is detached from the spool frame 30 and the spool piece 20 which is retained by the clamps 36 in the closed configuration the winch 72 is activated to lift the spool frame 30 and spool piece 20 within the recess 80 such that the lifting portion 41 is accommodated in the moonpool 62 fig1 the spool frame 30 is retained in this position by spool locks 66 provided on the pontoon 60 the sledge 12 is then recovered using the pre installed recovery line 98 and returned to the onshore build site where it can be reconfigured for use with another spool piece the pontoon 60 is then towed to the region of the spool piece 20 installation site as the spool frame 30 and attached spool piece 20 is towed through the sea 90 since the spool piece 20 is submerged and stored in the recess 80 beneath the pontoon 60 the spool piece 20 is transported beneath the splash zone thereby substantially protecting it from damage by wave action the spool piece 20 is also protected during transportation by the flow deviator skid 70 and the protective sidewalls 82 at the installation site the pontoon 60 is tied up to a deployment vessel not shown the deployment vessel is then manoeuvred into the required position above the installation site the heave compensated winch 72 accounts for changes in the tension of the winch wire 76 due to the heave of the pontoon 60 at sea 90 the spool frame 30 and the spool piece 20 are lowered from the pontoon 60 onto the seabed 94 fig1 where.