recently found my local park has cut back its reeds/bullrushes in the ponds, where they have been filtering out silt all year the pond around those cut down stems is super thick and muddy
pretty smelly pond mud but oh so irresistible.

Trouble is it won't be at all private or secluded, but if that doesn't bother you then go for it.

on a rainy day there are alot less people in the park,