This question is too vauge, or just generally doesn't make sense, unless the sraight line idea was correct. If amidships is taken to mean right angles, then this doesn't make sense, if H is headed on a straight line, then is hit by G from a right angle, then later F at a right angle, then we can conclude that both G and F are parallel to each other and could not have hit (in other words they would not have been able to have 3 colisions).
If we take amidships to mean any angle other than, 90, 180, 270, or 360 the we can say that H is traveling along a straight line, with G farthest ahead, followed by F, then E, then H. If we say that G is traveling near a 90 degree angle to H then F must be on an angle less than that, and E's angle would be smaller still. Thus H could either slow down, or speed up and presumably miss E. Of course this is assuming E and H's course will intersect with no action taken.
Basically my solution would be to barrel on heedlessly since you can't know anything about E for sure, and it doesn't matter if H and E colide anyways since nothing will happen (expept H might lose some pride).