After the cutscene, press [X] to jump down into the water, then follow Owen into the Aquarium. Once you’ve made it out of the water, head up the stairs and open the shutter, then make your way into the boat and look at the paintings with Owen.
Exit the boat and assist Owen up through the gap above the door, then crawl under the shutter and head upstairs. Here you’ll want to go over to the skeleton to view a short scene, then follow Owen downstairs and open the door. Finally, climb down the ladder and follow Owen through the cardboard box to view another cutscene.