Snapping turtles are more gregarious than I thought

Went for a kayak trip (in NE USA) and over 7 miles on the river I saw 79+ painted turtles, 6 snappers, 1 Plymouth cooter, 1 musk turtle, and possibly a couple others. (I only counted when I went upriver, to avoid duplicates)

The most exciting was seeing a group of at least 4 snapping turtles emerging from the mud. I have questions.

\-do they rebury themselves throughout the season, or did I witness their spring emergence?

\-do they congregate in the summer, or only in winter brumation spots?