Well, what can I tell you? I was close, but got no view of the grail itself.
Shooting through on the bus on a tight sched linking the Zambian eclipse and
a few days walking in Botswana, I had no opportunity to turn aside for those
few critical kilometres to look at the Chobe/Zambezi confluence. Glimpses
from a distance were obtained for both rivers, but not the hallowed waters at
their junction. The ground is quite heavily wooded thereabouts, and any hope
I had of a binocular view of the Bot/Zim beacons was dashed too. (I confess
long grass locally and a recent palpitating encounter with a puff-adder would
have made me very reluctant to bundu-bash into the trees, even if the
opportunity had presented itself.)
Maybe the following crumbs are of interest, though:
1) This is *flat* ground, with braiding clearly seen in the Zambezi a few km
below the confluence (from a high point in the road that gave me a glimpse
over the teak trees) and the Chobe a few km above the confluence (from the
back seat of a lurching Cessna flying upriver). Given that both rivers flood
seasonally, I'd say that there is very real potential for the thalwegs (and
therefore their junction) to change over fairly short time scales. This
brings the point raised by Peter S into sharp relevance - does a border
defined on the thalweg stay in place if the thalweg slips out from under it
at a later date? I'd assumed that the purpose of a thalweg border was to
allow both states equal access to the main channel, and therefore having the
border move with the thalweg would be reasonable, unless the treaty
specifically stated "line of the thalweg on such and such a date". But I
realise reason and international law may not come into close alignment on
this. So it might be that the border junction is *in principle* undefined at
present - if the thalwegs were not verified at the time (which they
apparently weren't) and if the boundary is deemed to lie at the thalweg
position *at the time of the treaty*, then the border can not now be
retrieved from the current river status. (Just my thought - poking my
ill-informed head over the parapet again.)
2) The Botswana-Zambia border exists by custom and practice, if nothing else.
The main drag through Kasane in Botswana is signposted south to Francistown
and north to "Zambian Border" - this is actually the Zambezi ferry that takes
you across to Kazungula in Zambia.
Sorry I can't give you a picture of the spot, though.

Jan: Belated thanks for your further information on the Sokh enclave - the
alleged Word-Wide Web hasn't arrived in the Linyanti Swamps yet, so I've only
just read your posting. Zambia is currently charging the same for a visa as
you report for Belarus - USD65. Last time I was there it was only 20 dollars,
but they were having a lively tourist season this month for the eclipse, and
I think were aiming to increase their GNP considerably off visa fees.

Grant