The thing is it isn't an narrow waterway, not really.
It's about 5 km across at the collision point.
Much narrower than the open sea which, even in coastal regions, has a spiky, ship-sinking rocky edge only in one direction, not both. Either way, I remember from the radio transcripts that the H.I. crew thought that they were too close to the limits of their lane to have room for maneuver (and that it was unnecessary because they weren't on a collision course with anyone, anyway, thank you very much).
Clearly, they had a very wrong picture of their situation, I suppose we can agree on that.