Skipper Neil King, of MacDuff, Moray, was in charge of the Prospect last August when she ran aground on Skibby Baas rocks at Lerwick Harbour in Shetland.
Mr King and his three crew were rescued by Lerwick's lifeboat, but despite attempts to tow the vessel to safety, she soon sank in 50 feet of water. In a report by the Marine Accident Investigation Branch (MAIB) on Wednesday, it was claimed that as well as being distracted by a phone call, Mr King's judgement may have also been hampered by alcohol drunk earlier that day.
It said: "The skipper had not effectively planned and monitored the vessel's passage. He had become distracted in continuing a telephone conversation while altering the vessel's course. It is possible that his performance was adversely affected by alcohol."
Weather conditions on August 5 were not considered a reason to cause the crash, as it was sunny with good visibility, a force two wind and a "smooth" sea-state.
In their report, the MAIB recommended Mr King, attend a navigation skills refresher course.