It’s common assumption that when the iceberg was sighted and realized on the bridge that first officer Murdoch ordered both wing engines to ‘full astern’(the turbine could not be reversed). However there’s no real proof of this. This idea comes third hand, from fourth office Boxhall, who said that’s what he heard Murdoch telling Captain Smith once he arrived on the bridge. But testimony from the quartermasters as most notably from crew in the boiler/engine rooms doesn’t support this. They record an order of ‘stop’. Following the collision(and the following may be a bit off since it’s been quite a while since I’ve looked into this) the engines were put to slow astern(I imagine to slow the headway of the ship) followed by them being put to ‘slow ahead’ by Captain Smith for a few minutes after the collision(his reasons why we’ll never know, it is possible he was checking for shaft damage to the propellers given the side blow with the iceberg). Following that(I imagine when word started coming up the holds were taking on water) the Titanic’s engines were put to stop for the last time not long after the collision.
And of course this all comes with the fact that even if we take the ‘full astern’ version at face value, the window of time was just far too small to throw the engines which had a full head of steam going ahead into reverse. But the point of this post is that never happened to begin with.