Yeah, some wading is possible, but one of the more persuasive arguments against the old vision of sauropods submerging their whole bodies in water to “support their weight” is the realization that, once the animal is submerged and using his long neck to keep his head above water, the water pressure that deep would make it impossible to inflate the lungs and breathe.
The fact that they had air sacs and hollow bones means they may have been too buoyant to submerge at all. And the hollow bones strongly argue against them being aquatic to any extent, since most aquatic animals have dense bones to help them submerge.
Sauropods (Brachiosaurus, Diplodocus, and their ilk – the giant long-necked ones) had extensively pneumatic skeletons. If anything, they wouldn’t be able to not swim in water over a certain depth. Y’know, just like that other large long-necked dinosaur.
Well, floating on top of the water would mean they wouldn’t have a problem with breathing against the pressure, and it’d still support at least part of their weight (though the bottom of the torso would still need to support the top of the torso).
I would think they didn’t float very high. How high do whales or humans float? I recall that a human can breathe through a snorkel for three feet. Perhaps they floated with their lungs slightly underwater.
I am still amazed seeing elephants paddle around with those flat elephant feet.
