probably not. At 6' of neck length, they're looking at roughly 2.5psi worth of hydrostatic pressure to overcome. Probably another few feet from lungs being lower than neck.

It's not technically an impossible feat, but animal lungs are very generally not capable of that kind of vacuum pressure. Humans, for comparison, usually peak at around 1psi. The problem is that you're not creating that pressure with muscles -- it's from the bones in your ribcage being pre-sprung to expand; your muscles are just letting them do that. E: Right now there's another askscience thread on literally this exact topic. It's better than my sentence and a half..

They have a very hard time and they generally don’t go in water because they can’t swim. Another animal that can’t really swim is a hippo. An elephant can be in water over its head because of how their muscles and ligaments and whatnot hold their lungs. The water pressure does nothing to their lungs. Unlike with giraffes.