Bottom is a type of Supply. Bottom is related to Cotton. Cotton is related to Short. Short is related to Sleep. 
Essential is related to Oxygen. Water is part of Oxygen. you are likely to find Water in/at/on Spit. 
Supply <--IsA-- Bottom <--RelatedTo--> Cotton <--RelatedTo--> Short <--RelatedTo--> Sleep 
Essential <--RelatedTo--> Oxygen <--PartOf-- Water --AtLocation--> Spit 