I think the idea of being trapped in a confined space kilometers under the sea has a visceral effect on the imagination that a boat voyage on the surface doesn't, regardless of how tragic the outcome is in both events. It pokes and prods many of our deep phobias.
Similar stories like the Thai boys trapped in the cave, or the Chilean miners, had a similar effect.
A bit like "Snakes on a plane". Again, trapped with your phobias.