Rule 3: If a detail isn't mentioned, then it doesn't matter.
The scoring conditions for the Water mission do not mention any particular bottle of water, so that detail doesn't matter.
Update 20, TSUNAMI WAVES DON’T COUNT AS WATER, confirms that the little water bottles are the important items:
--The only models that count as water with people are the little water bottles. The tsunami cylinders don’t.
Update 8, PEOPLE WITH WATER, clarifies that the scoring condition has us count people, and not whether there are multiple water bottles:
-- “People with at least one water = 15 points each” means the more people who have water, the more points you get. You get 15 points per PERSON with [any amount of] water. Examples: 1P+1W=15, 1P+2W=15, 3P+2W=45