Preservation of the "Mary Rose" and her contents was an essential part of the project from the start. Though many artefacts, especially those that were buried in silt, had been preserved, the long exposure to an underwater environment had rendered most of them sensitive to exposure to air after recovery. Archaeologists and conservators had to work in tandem from the start to prevent deterioration of the artefacts. After recovery, finds were placed in so-called passive storage, which would prevent any immediate deterioration before the active conservation which would allow them to be stored in an open-air environment. Passive storage depended on the type of material that the object was made of, and could vary considerably. Smaller objects from the most common material, wood, were sealed in polyethylene bags to preserve moisture. Timbers and other objects that were too large to be wrapped were stored in unsealed water tanks. Growth of fungi and microbes that could degrade wood were controlled by various techniques, including low-temperature storage, chemicals, and in the case of large objects, common pond snails that consumed wood-degrading organisms but not the wood itself.