Premise:
"I watched her as she mounted me and began to move like waves of sand on the wind."
Hypothesis: She got on top of me.

yes

Premise:
"Offshore, the professional fishing business which was once a major source of income in Ibiza has dwindled significantly."
Hypothesis: The fishing started to decline as tourism increased.

it is not possible to tell

Premise:
"Its volume declined from 10."
Hypothesis: The volume went down from 10
yes