A SAG has a fairly broad definition--two or more whales within
a body length interacting at the surface--but typically, the
SAG is comprised of one female and a number of males competing
with each other in order to mate with her. Some SAGs are
extremely active, with a lot of rolling and white water,
whereas others are more sedate. The number of animals in a SAG
can range from two or three to more than 40!


http://www.neaq.org/education_and_activities
/blogs_webcams_videos_and_more/blogs/bay_of_fundy/2008/08
/14-surface-active-group-sag.html