tide
They left port on the ebb tide.

against an/the ebb
It was difficult sailing upstream against a strong ebb.

on an/the ebb
By this time, the tide was on the ebb.
We floated away from the beach on the ebb.

with an/the ebb
They went out to sea with the ebb.

the ebb and flow of sth
the natural ebb and flow of water
We see a constant ebb and flow of jobs. (figurative)

away
He knew that his life was ebbing away.

slowly
Calla felt her fear slowly ebbing away.

begin to
Her strength began to ebb.

seem to

Ebb is used with these nouns as the subject:
strength, tide