Body temperature? How can that be an aquatic factor? Well, Moore seems to think it is. He claims that "AAT proponents often make several claims about mammalian body temperatures". He doesn't give us a hint as to who made such a suggestion and after spending some time researching I found that it wasn't something Hardy discussed, or even Elaine Morgan in her five books on the subject. Verhaegen has used published data on comparative body temperatures to  argue  that humans would appear to be very different from savannah animals and, if anything, more similar to slow moving aquatic mammals in this respect. Again Moore's 'claims' are exaggerations, placed out of the context of the detailed argument and highly selective. He criticises portrays Verhaegen's view on something when Morgan's is sound and vice versa but he doesn't inform the reader who's making the claim so that it sounds like it's all coming from the one, somewhat crazy, source.

On this page Moore also reveals his true thinking of the AAH a couple of times. The first claim was written like this: "The body temperature of normal, healthy humans doesn't fluctuate, while that of terrestrial mammals does", implying that Moore thinks the AAH is arguing that humans were not even terrestrial.

On this page, in nearly 1,800 words, Moore makes two (again unattributed) claims about the AAH on the subject of body temperature. Both exaggerate the claim by a single AAH proponent (Marc Verhaegen) to an absurd and unsupportable level.

Body Temperature and the AAT: Does the human condition indicate an aquatic past?
Moore starts this page with two claims he claims AAT proponents make about body temperature:

1. "The body temperature of normal, healthy humans doesn't fluctuate, while that of terrestrial mammals does."
    
2. "Normal human body temperature is like that of whales, rather than our primate relatives or other terrestrial mammals."

No citation in sight, again but it is noticeable here that Moore seems to have let his gross misunderstanding of the hypothesis slip out for all to see.

Did you notice, in the first point: "while that of terrestrial mammals"? It appears, doesn't it, that Moore is assuming the AAH is proposing that humans were not terrestrial. He's not pointed to any citation where a proponent of the AAH has gone that far, but Moore has taken that step himself on their behalf.
The second claim would be a logical position to hold if one  really did believe that humans were aquatic mammals. But, of course, nobody thinks that.

Moore then goes on to tell us that although humans exhibit a lower range in body temperature than some terrestrial animals, this is because they tend to have special adaptations (heat exchange mechanisms like the 'carotid rete') to allow it. Moore again demonstrates his ignorance when he adds "AAT proponents consider these facts to be evidence that we did not evolve on land."  At the risk of sounding like a cracked record, this is not what AAT proponents consider. The AAH, remember, proposes that man was more aquatic in the past, not that our ancestors were ever aquatic in any real sense.

Moore then goes on to answer what he calls "the AAT question regarding our thermoregulation." It turns out to be a rather simple question that he has selected (possibly out of many) from his conversations on internet newsgroups. He does not attribute the question to anyone nor does he attempt to answer other, more difficult ones one might think of on this subject like, for example, why do humans throw away water more than apes as a means of keeping cool through evaporative sweat cooling? In what evolutionary setting is that most likely to have evolved?

Instead, he deals with this one:

If we were on the savanna for the millions of years as you say, and did not have an intervening period of "aquatic-ness", instead evolving with the other savanna creatures, why then did we not end up evolving the same way?"

Easy. And he answers it pretty well too, basically, arguing that we are primates and so evolved mechanisms that were essentially different from savanna ungulates.

Why do people harbor the incorrect idea that human body temperature doesn't fluctuate?
In the next section Moore decides to answer this question. Again, no attempt to cite anyone who actually does harbor such a view, but never mind that.

Moore quotes from Smith (1985) which spells out that human body temperature varies in lots of ways by as much as 1.5 degrees. He then finishes the page by comparing human body temperature to that of primates, whales and bats.

As bats, apparently, have the same body temperature as humans he ends the page by suggesting that maybe some people might think that in the past we used to be able to fly. It's meant to be funny, I think.

Moore's counter-arguments to the claims would appear to be straightforward, then. But who exactly made these claims?
I certainly didn't remember reading any such argument, but perhaps I just missed them. As no citation was given, as usual, I was left to have to go searching through all the literature I have on the AAH to try to find out if this was not just another example of Moore misrepresenting the case for the AAH.

Hardy made no mention of this in his original article and it is not a major topic heading in any of Morgan's books, so it was necessary to search through the index looking for anything vaguely related.

I couldn't find any reference to human body temperature in relation to an argument favouring a more aquatic past in her first book 'The Descent of Woman' (Morgan 1972) nor 'The Aquatic Ape Theory' (Morgan 1982).
In 'Scars of Evolution' (Morgan 1990) the topic does sort of appear, in a section headed 'The Aquatic Ape Theory - The Counterarguments' but Morgan is not arguing that only humans among terrestrial animals have core temperatures that do not fluctuate but that in cold water humans would just swim for shorter periods to stop their temperature falling too far.
In 'Descent of the Child' (Morgan 1994) she also mentions body temperature, but only in the context of child birth. She writes "A full-term infant has a temperature slightly higher than its mother's, around 98.8 degrees Fahrenheit. There is an immediate drop of 3 degrees in the first hour after birth; within two hours it may have dropped 5 degrees, and the baby can do nothing about it." (Morgan 1994:90). Moore, remember, told us that AAT proponents think that "the body temperature of normal, healthy humans doesn't fluctuate, while that of terrestrial mammals does." Something doesn't quite add up here.
And in her last book 'The Aquatic Ape Hypothesis' there was no mention of it that I could find either.
Perhaps other AAH proponents have been arguing for this. I checked out a few likely papers by Marc Verhaegen and found a whole section entitled 'Body Temperature' in Verhaegen (1991:183-185). It is probable, from reading the piece, that this is what Moore was thinking about when he  

wrote his page, but like a headline in a tabloid newspaper, Moore does Verhaegen a grave injustice.
Firstly, Verhaegen doesn't suggest that human body temperature doesn't fluctuate just that, compared to savannah animals, it does not fluctuate as much. He cites several papers to back this claim up. If Moore was interested in scientific objectivity perhaps he might have mentioned them and gone to the trouble to refute that source data, but he didn't bother with that.
Secondly, although Verhaegen does suggest that "a normal temperature as low as man's is found chiefly among the larger aquatic mammals" (Verhaegen 1991:185), he qualifies this by "if we exclude the group of slow-moving mammals listed above" and that "hunting or hunted pinnipeds have a body temperature like ours or slightly higher" (Verhaegen 1991:185.)
His main point in that paper is, as usual with Marc, to contest the long prevailing notion that man had evolved on the savannah. He concludes "in other words, humans have a normal temperature resembling that of sea mammals, lower than most terrestrial ones, and markedly lower than that of any active savannah species." (Verhaegen 1991:186)
Verhaegen did not make any comparisons with the body temperature of primates, and perhaps he should have done, but Moore's claims are clearly an exaggeration at best and a gross misrepresentation, at worst, of the AAH argument.

References:
Hardy, Alister (1960). Was Man More Aquatic in the Past?. New Scientist Vol:7 Pages:642-645.

Morgan, Elaine (1972). The Descent of Woman. Souvenir Press (London)

Morgan, Elaine (1982). The Aquatic Ape Theory. Souvenir Press (London)

Morgan, Elaine (1990). The Scars of Evolution. Oxford University Press (Oxford)

Morgan, Elaine (1994). The Descent of the Child. Penguin Books (London)

Morgan, Elaine (1997). The Aquatic Ape Hypothesis. Souvenir Press (London)

Smith, Anthony (1985) The Body, Routledge

Verhaegen, Marc (1991). Human Regulation of Body Temperature and Water Balance. In: Roede, Machteld; Wind, Jan; Patrick, John; Reynolds, Vernon (eds.), (1991). Aquatic Ape: Fact of Fiction: Proceedings from the Valkenburg Conference. Souvenir Press (London)

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