The white pearls, yes, I'd say freshwaters.
I'm not sure the dark 7mm pearls are even real pearls, not from those photos. Too many reflections, too many pearls out of focus-- hard to see them well. Maybe take some more photos in diffuse natural light?
Try these tests:
1. Rub two of the pearls together (gently) to see if they are smooth or gritty feeling. Smooth = imitation pearl coating; gritty = real nacre. If you're gentle this shouldn't scratch them, but to be safe, I like to use pearls near the clasp for this test.
2. Glass imitation pearls will feel a bit warmer than real pearls when held against your lips (which are very sensitive to temperature.) Compare how warm or cool these are with a real strand of pearls, but only after both strands have been in the same temperature environment for 30 minutes or so, to reduce variables.
