Hole can be used for Water. you are likely to find Bottom in/at/on Water. Bottom is a synonym of Bed. 
Could is related to May. May is related to Will. Willing is a form of Will. Willing is a synonym of Voluntary. 
Hole --UsedFor--> Water <--AtLocation-- Bottom <--Synonym--> Bed 
Could <--RelatedTo--> May <--RelatedTo--> Will <--FormOf-- Willing <--Synonym--> Voluntary 