A man is going down a river in a kayak.
A person is kayaking down the river
A man is a person.  Kayaking down, implies going down a river.
exists e1 s1 x1 x2 x3.(in(e1,x3) & n_kayak(x3) & a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_go(e1) & n_river(x2) & n_man(x1))
exists e1 s1 x1 x2.(n_river(x2) & a_down(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_kayake(e1) & n_person(x1))