that's a good example, it's a good trick to use texture offset for animated water,
rivers, or water fall.

Apply texture (seamless) on your 3d model

Make sure its UV mapped of course

Go on Animation view then :
Make sure you are on the first (1) frame on the timeline

Go under texture tab -> Mapping, and put your cursor over "Offset"

(Side note, hold left lick on X or Y offset to see the real-time results !)

Press "i", this will add a keyframe at frame 1, note that offset will turn yellow and there will be 3 options added on the graph editor, like you can see here :

On Graph editor window, Uncheck two of the offsets (depends on your needs, here i just enabled Y ) and move on last frame of the Timeline (200 in this case)
Put Offset Y on 1.00 , then put your mouse over Offset again and press "i", that's adding another keyframe at frame 200.

So far,
we have 1 keyframe at frame 1 with Offset Y : 0.00
and 1 keyframe at frame 200 with Offset Y : 1.00 (from 0 to 1 = one complete loop)

Ok now, on the graph editor window, go on Key -> Interpolation mode -> Linear
That will change the curved line to a straight one

If u don't fucked up, graph should look like this :

Now export with maratis exporter (dont forget to activate animation)
And thats all.

In maratis, some examples :

Simple texture on an object (i failed frame rate of the gif here è_é dont worry its smoother in maratis)

Scrolling texture + static normal on a plane

Scrolling texture + scrolling normal on a plane