Water-neutral means that the products are manufactured in a water-friendly way, it's all about reducing and offsetting the impacts of water footprints.
Bamboo can be a very sustainable crop, it is a fast-growing grass, that requires no fertiliser and it self-regenerates from its own roots, so it doesn't need to be replanted (unlike most other materials). When comparing bamboo to cotton cultivation for example, cotton requires large amounts of water, pesticides and is labour intensive, so the advantages of bamboo are clear.
Hydrophil use bamboo, a natural ingredient that grows without artificial irrigation.
They only use paint that is produced without mineral oils or other chemical additives and therefore leaves no residues in the drinking water or groundwater during composting.