The dinocephalian synapsid,
Moschops (Fig. 1), looks like it could not bend its neck down to take a drink of water from the shoreline, giraffe-style.
Figure 1. Stiff-necked Moschops did not need to lean down, giraffe-style, to drink water. It could just wade into chin deep water.
But Moschops could wade
into chin-deep water, maybe where it’s plant diet sprouted. Okay, no big deal, but I’ve wondered this and the simplest answer did not come to me for some time, probably because I was giraffe- and wildebeest-biased. Watching my dog walk knee deep into a pond cleared the air for me.
The Pterosaur Heresies 
occam’s razor at work?
Or, Moschops could move its hands as far backwards as it could, and it’s neck would be able to bend down to the water.
Moschops would not do that, as their body plan would cause this to result in some serious pain.
Then their’s the possibility that they jumped into the water. I came up with this hypothesis after reading your post and then seeing my cat jump off a chair.