People are taking pictures across the water.
the people are a couple
The word "people" can refer to any number of people, as long as there is more than one person present. Not all groups of people are a couple.
exists e1 x1 x2 x3.(n_water(x3) & across(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_take(e1) & n_picture(x2) & n_people(x1))
exists p1 x1.(n_people(x1) & exists x2.((x1 = x2) & n_couple(x2)))