Drakkar event brings players extremely close to a Mastery point but not close enough to claim it. The reason is that the entrance to it is in a completely different place.
Whispering Depths Mastery point is geographically very close to the place where you fight Drakkar, leading many Guild Wars 2 players to desperately attempt to find a way to it, following the completion of the event. They can't find it because the point is located in a different cave and the entrance is located just east of Whispering Depths, in Frigid Dunes.
You will find several Sons of Svanir inside the cave - you can either kill or just run past them on your mount, they are not much of a threat. The only exception is the Champion that spawns if its event is active. He will be located in a large section of the cave that has several niches in it.
Take the second niche to the right, you can completely avoid Champion's aggro here.
You will find a Raven Gate in this niche, use it and you will enter a jumping puzzle. Simply take the door with two lit up torches to your right and start jumping across the planks and icy platforms. You will soon see another similar door and that's where you need to go.
Once you're through the second doorway, keep going the way the jumping puzzle leads you and you will end up the bow of a broken ship. At this point, you can see where the place of power for the Mastery point is.
Climb as high as you can on the bow and jump to the right side, relative to the bow, and continue jumping through the rest of the puzzle until you reach the Mastery point.