For what reason does the narrator worry in Chapter 26 about the eventuality of the old man's boat sinking completely?

The narrator continues to observe the boat sinking a little more each day and in Chapter 26, she shudders at the thought of the day when it may be completely submerged under the water. Her apprehension comes from the fact that she wonders if without the sight of the boat, she will retain the fond memories she has of times she and the old man spent together on the vessel where he had lived. The narrator states that her heart aches when she thinks about the day the boat will sink, saying, "Would I remember how we had eaten cake in the wheelhouse? Or made our plans to build the hidden room? Or stood on deck, leaning against the rail, watching the sunset?" (255).