VTRANS160100 - Pilotage, salvage, towage and surveying services: Law
The law applying the zero-rate to pilotage, salvage, towage and surveying services is in the VAT Act 1994, Schedule 8, Group 8, items 7 to 9:
7. Pilotage services
8. Salvage or towage services
9. Any services supplied for or in connection with the surveying of any ship or aircraft or the classification of any ship or aircraft for the purposes of any register.