UPDATED 8.24PM: A third soldier facing military charges over the drowning of Private Matthew Ross in a training accident in 2012 has been found guilty of failing to comply with written orders.

A summary trial has found the sergeant, who has name suppression, was commander of a boat that was not responsible for safety when Private Ross fell overboard from another boat.

However, it's ruled that he was operating the boat with less than the three suitable people required on board earlier in the day.

The sergeant has been fined 700 dollars.

Earlier today two others, Sapper James Larsen and Corporal Timothy Goodall, were found not guilty of negligence charges.

Corporal Goodall pleaded guilty to a charge of failing to perform a duty and was fined 500 dollars.