When you regain control, move ahead without stopping. When time slows down, jump to have Lara grab onto a rope.
As the games suggests, you'll now need to make use of the rope ascender to speed up the rope ascent. Hold the action button and keep holding it until the game triggers another cut-scene.
You're free to move on. When you reach the deck where the mini boss battle took place, head for the crates Lara can scramble up. Grab onto the rope and hold the action button again to return to the beach much quicker. Use the last rope to return near the bunker (reward: 100 XP).
Approach the bunker and shoot a rope arrow to pull the above object towards you (hold the action button), then drop down the hole. This will trigger another cut-scene and let Lara acquire a Document (collectible).