Roland Wilson, 32, a lieutenant in the RN Reserves, was convicted of failing to keep a proper lookout and two counts of impeding the passage of a vessel following a five-day trial at Southampton Magistrates' Court.
The court heard Wilson, of Stanley, Perthshire, was in charge of the 33ft yacht Atalanta of Chester when it collided with the 870ft Hanne Knutsen on the first day of the regatta in August 2011 .
The accident happened despite the married father-of-one having seen the tanker from five miles away.
Footage of the incident, in which one crew member suffered minor head injuries and another abandoned ship, was posted on YouTube and has been viewed more than 900,000 times.
District Judge Anthony Callaway fined Wilson £2000 for failing to keep a proper lookout and £500 for each of the two offences of impeding the passage of a vessel and ordered him to pay a £15 victim surcharge. The maximum penalty was £5000 on each charge.
But he was ordered to pay the full costs of the prosecution which totalled £100,056. The court heard a substantial part of these costs was to pay expert witnesses who examined and reconstructed the routes taken by the vessels in the run up to the crash.
Judge Callaway said: "Given the nature of the collision, it is quite inevitable that the prosecution obtained substantial input from technical and skilled sources and that of course requires money."
During the trial, Charles Row, prosecuting, said Wilson - who owned and skippered the yacht - sailed the boat, which had seven other crew members, "perilously" into the path of the 140ft-wide Hanne Knutsen.
Mr Row said Wilson broke shipping bylaws which required him to maintain a moving prohibited zone of 1094 yards in front and 109 yards either side of a vessel more than 492ft long.
Wilson told the court the tanker had sounded its horn to indicate it was to turn to starboard but then did not carry out the manoeuvre, leaving him in a dangerous position in front of the vessel.
The trial heard a motor vessel, the Joy C, had lost power and caused the Hanne Knutsen to change its intended course.
Wilson, a physics graduate from Durham University, told the court he joined the Royal Navy in 2006 and left in February this year, but still remains a reservist.
Judge Callaway said he respected Wilson's crew, which included highly-ranked former RN officers, but ruled the skipper had made the wrong decision and placed his yacht and the tanker in danger. He said: "This was a serious yacht crewed by serious people in the regatta for a serious purpose and well-equipped in terms of experience and ability to deal with any situation.
"This was not some Saturday afternoon jaunt by some inadequate vessel crewed by the inexperienced and foolhardy who have no business being on the water for their own good and everyone else's. Frankly, I doubt any other crew in the 2011 regatta or at any other event could have fielded a better team, at least on paper.
But he added: "The skipper has the ultimate say and carries responsibility accordingly and that is the position for time immemorial.
"Fortuitously, there was no loss of life. This was a serious incident in itself. The potential for an even greater consequence was apparent."
Outside court, Wilson said only: "I have no comment."