They stressed the importance of interaction with seawater, believing that it was necessary for the formation of coal balls.[12] Some supporters of the in situ theory believe that Stopes' and Watson's discovery of a plant stem extending through multiple coal balls shows that coal balls formed in situ, stating that the drift theory fails to explain Stopes' and Watson's observation. They also cite fragile pieces of organic material projecting outside some coal balls, contending that if the drift theory was correct, the projections would have been destroyed,[13] and some large coal balls are large enough that they could never have been able to be transported in the first place.[14]