A group of young people walking across a stepping stone path in water.
A group of people are in the mountains.
Just because young people are walking across water does not mean they are in the mountains.  Bodies of water can be in almost any geographical area.
exists e1 s1 s2 x1 x2 x3 x4 x5 x6.(a_topic(x1) & of(x1,x2) & in(e1,x6) & n_water(x6) & across(e1,x4) & n_path(x4) & of(x4,x5) & n_stone(x5) & a_stepping(s2) & Theme(s2,x4) & Actor(e1,x3) & v_walk(e1) & (x2 = x3) & n_people(x2) & a_young(s1) & Theme(s1,x2) & n_group(x1))
exists p1 x1 x2 x3.(n_mountain(x3) & in(x1,x3) & of(x1,x2) & n_people(x2) & n_group(x1))