Final answer:
Water is not effective against certain hardy organisms and cannot remove water molecules from small pores due to cohesive forces. Water scarcity is a global problem despite its abundance.
Step-by-step explanation:
Water isn't very effective against certain hardy organisms, such as the protozoan parasite Cryptosporidium, which can survive in contaminated drinking water even when treated with chlorinated compounds. Additionally, water is not effective in removing water molecules from small pores due to the cohesive forces of water outweighing the force of gravity. Finally, water scarcity is a significant global problem, with water scarcity being the world's most serious resource problem despite water being almost everywhere but often unusable or inaccessible.