Two decisions hide inside one ship name
Do you want the vessel sitting in a sea scene, or a freestanding object with the hull below the waterline visible? Answer that before assuming that a larger scale settles the question. Tamiya identifies 31113 as a 1/700 Waterline model, with a stated length of 375 mm. Its presentation suits a scene that meets the ship at the waterline.
The larger kit keeps the choice open
Tamiya's 1/350 Yamato, item 78025, is listed at 752 mm long. Crucially, the manufacturer says it can be assembled in either full-hull or waterline form. ‘1/350’ therefore is not shorthand for ‘the lower hull must be displayed’. It is possible to choose the larger model and still intend a sea-level composition.
That changes the practical question. If the aim is a large waterline scene, rejecting 78025 merely because product photography shows a full hull would discard an option that the manufacturer explicitly provides. Conversely, 31113's Waterline label should not be read as a promise of the same two-format choice.
Draw the finished scene at its real length
Mark out 375 mm or 752 mm on the intended surface, then add the scene around it. Those are the documented model lengths, not complete dimensions for a base, case or sea diorama. The larger option changes the composition substantially even when both models meet an imaginary sea at the same level.
The useful selection is a combination: the documented assembly format you want and the space that its particular scale occupies. These two Yamato kits make that combination clearer than a simple rule that small means waterline and large means full hull.
Sources & further reading
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