Why Did Isildur Cross the River?

[Inziladun]

Originally Posted by alatar

Are we asking why Isildur, when under attack, went for a swim? Or why he was doing his Middle Earth victory lap? If it's the former, I'd think that it not only might have saved him, but aided his escape as don't the evil folk fear water, to some extent?

Basically, it appears that if Isildur had simply chosen to journey on the west side of Anduin, the swim across would not have been necessary. It looks to me as if he deliberately took the long way around.
Now, it can certainly be argued that if he hadn't gone for a swim in the Anduin, the Ring would not have been lost, and the whole of Third Age Middle-earth history would have been re-written. Fair enough.
Be that as it may, I simply don't see any likely reason why he chose the route he did.
If the Ring itself played a part, why didn't Isildur's Men, and especially his sons, question his decision to journey east of the Anduin? Going on the western side would have put them nearer the Mountains, and in a position where they could have received help from Lórien and Khazad-dûm. And as I said earlier, there was the Redhorn Gate that they could easily have used to pass the Mountains.