Moisture Loving (Bog) Plants
Moisture Loving Plants, as the name implies, love to be moist. However, they are different from shallow water marginal plants in that they usually do not tolerate having their crowns submerged for long periods of time, particularly in winter.
Moisture loving plants are perfect along the edge of a pond or streambed just barely out of the water, perhaps placed between rocks that line the water, so they can put their roots into the water. Most also do well planted along the edge of a waterfall, particularly if small pockets are built in to accommodate them. We heard it explained in a lecture once that these plants "like their ankles dry and their feet wet", which is a cute way to phrase it.
Sometimes due to just the right combination of conditions, moisture loving plants may tolerate permanent immersion of their crowns. This will succeed more frequently if planted in shallow water in the moving water of a streambed, due to the higher oxygen content of the water combined with water's natural tendency to dilute by-products of stagnant conditions.
Most sellers do not differentiate between moisture loving, bog, and shallow water plants, leaving buyers to find out by trial and error. We want to maximize successful growing, so we do our best to educate buyers on what the plants like!