A surfer rides a medium-sized wave.
The man is trying his hand at surfing while the water is relatively calm.
A medium sized wave does not mean calm.
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_wave(x2) & a_medium-sized(s1) & Theme(s1,x2) & n_surfer(x1))
exists e1 p1 x1 x2 x3 x4.(n_water(x4) & n_hand(x2) & of(x2,x1) & n_male(x1) & n_man(x1) & exists s1.(r_relatively(s1) & Theme(s1,x4) & a_calm(s1)) & while(e1,p1) & at(e1,x3) & n_surf(x3) & Theme(e1,x2) & Actor(e1,x1) & v_try(e1))