Looking at the state of the water, Alexander found himself hesitating to take the last step.
With all the obstacles in front of him, jumping ship did not seem to be at all a prudent option.
There were patrol ships with archers cruising over the freezing water, and his destination lay several kilometers away, which he would be asked to cover while basically wearing a straitjacket.
A straitjacket that Alexander was unable to take off due to the threat of any potential stray arrow or javelin shot towards him, for there were bound to be some potshot coming along his way when he tried to escape.
And if by any bad luck one of them were to hit, without the armor he might perish to a shot that he otherwise might have survived.
Alexander was unwilling to take such a huge risk.
Neither was he sure he could make it there with it on.