zoology - Can all mammals swim?

When I checked it seemed trivial to answer: yes, all mammals can swim. But research on the internet provided different information. I found:

Of each hit, I found other hits that claimed the reverse, sometimes with proof. Common sense tells me all mammals can swim, but is this true?

Answer

With respect to the giraffe claim, this article seems relevant:

D. M. Henderson, D. Naish, Predicting the buoyancy, equilibrium and potential swimming ability of giraffes by computational analysis, J Theoretical Biology 265 (2010) 151-159.

It cites several non-"random person on the internet" claims that giraffes cannot swim:

It is generally thought that giraffes cannot swim, but relevant observations are few. Shortridge (1934) and Goodwin (1954) state that giraffes were poor waders and unable to swim. Crandall (1964) discussed a case where a captive giraffe escaped from a carrying crate, ran to the end of a jetty, and fell into the water. The animal reportedly sank without making any attempt to swim. MacClintock (1973, p. 54) stated ‘Giraffes cannot swim. Rivers are barriers they do not cross’. Wood (1982, p. 20) noted that ‘Because of its extraordinarily anatomical shape the giraffe is one of the very few mammals that cannot swim – even in an emergency! Deep rivers are an impassable barrier to them, and they will avoid large expanses of water like the plague’.

They then go on to show that a model giraffe could plausibly swim, writing: "For practical and ethical reasons we are unable to use live giraffes..."

They conclude:

In summary, the results and speculations of this study show that it is not impossible that a giraffe could propel itself in water, but in terms of energy efficiency relative to that of the horse, it would appear that the costs of aquatic locomotion might be too high. It is reasonable to expect that giraffes would be hesitant to enter water knowing that they would be at a decided disadvantage compared to being on solid ground.