(At issue here is how sand dunes are formed in such deep water.
(At issue here; is; how sand dunes are formed in such deep water) Context(At issue here is,List([1, 17))):(sand dunes; are formed; L:in such deep water)
At issue here is,List([1, 17))
At issue here sand dunes
is are formed
how sand dunes are formed in such deep water
L:in such deep water