Tunnel is related to Dark. Dark is related to Grave. Grave is related to Monument. 
Shark is a type of Expert. Shark is related to Sea. Sea is related to Captain. 
Tunnel <--RelatedTo--> Dark <--RelatedTo--> Grave <--RelatedTo--> Monument 
Expert <--IsA-- Shark <--RelatedTo--> Sea <--RelatedTo--> Captain 