Assertion: porpoise's flipper | /r/ObjectUse | used for steering
Facets:
value: mainly
type: DEGREE
Source sentences:
text: When swimming, they move their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering.
text: When swimming, they move their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering.
text: Porpoises swim by moving their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering.