An advantage of the closed deck was that it protected the Korean sailors and marines from small arms and incendiary fire.
Six Korean sailors were also injured during the fight; three critically.
South Korea's defense minister has estimated that more than 30 North Korean sailors were killed or wounded in the battle.
"Eight hundred North Korean sailors come here each year," the analyst said.
The North Korean sailors thanked the members of the unit before proceeding to India.
In 1999, at least 17 North Korean sailors were killed in a firefight there.
Three South Korean sailors were wounded but they were able to save their ship from complete destruction.
On the other hand, a defector said about 10 North Korean sailors were killed in action.
Two South Korean sailors were killed and four injured.
The North denies involvement in the incident, in which 46 South Korean sailors died.