premise: The crew shells are passing under marker 7, with the nearest shell in front by a good margin.
hypothesis: a race of some sort is underway
explanation_1: You can not infer there is a race.
explanation_2: The first sentence could be describing a variety of activities with markers, not necessarily a race.
explanation_3: There are two shells moving in one direction, but that doesn't necessarily mean the two are in a race or that one is underway.
premise_logic: exists e1 s1 s2 x1 x2 x3 x4 x5.(n_shell(x1) & n_shell(x1) & r_most(s1) & a_nearest(s1) & Theme(s1,x1) & of(x1,x2) & n_crew(x2) & with(e1,x1) & in(x1,x4) & by(x4,x5) & n_margin(x5) & a_good(s2) & Theme(s2,x5) & n_front(x4) & under(e1,x3) & n_marker(x3) & n_date(x3) & a_date_day_07(x3) & a_date_day_07(x3) & Actor(e1,x1) & v_pass(e1))
hypothesis_logic: exists s1 x1 x2.(Theme(s1,x1) & a_underway(s1) & of(x1,x2) & n_sort(x2) & n_race(x1))
premise_sim: exists e1 s1 s2 x1 x2 x3 x4 x5.(with(e1,x1) & v_pass(e1) & under(e1,x3) & r_most(s1) & of(x1,x2) & n_shell(x1) & n_marker(x3) & n_margin(x5) & n_front(x4) & n_date(x3) & n_crew(x2) & in(x1,x4) & by(x4,x5) & a_nearest(s1) & a_good(s2) & a_date_day_07(x3) & Theme(s2,x5) & Theme(s1,x1) & Actor(e1,x1))
hypothesis_sim: exists s1 x1 x2.(of(x1,x2) & n_sort(x2) & n_race(x1) & a_underway(s1) & Theme(s1,x1))