There some locations that really nicely match your list of requirements in Australia, (Eg Lake Eyre, last had water in 2019, was full in 2001) but that isn't really a surprise desert, and if you asked me in 2018 I would've called it a desert, and no-one is silly enough to lose their boat in it.
Same with the dead sea, and the Aral sea; these areas are basically already deserts, or are nearly there. So, I don't think they match. You want a nice, lush location, that could become a desert very soon.
Other areas around Australia are candidates, but the governments have surplus desalination capacity to supplement agriculture in this case (my city has a spare desal plant that is running at 10% capacity just in case climate change cranks up suddenly), so government action could mitigate desertification. (At least in the small areas of Australia that aren't already desert).
So you really also want an area without a government able to mitigate desertification, that is lush now, and could suddenly dry up by 2080.
Also, if I (western middle class) lost my boat cause the lake dried up - I'd save up a bit and hire a crane and go grab it. So, we need an area where people don't have the means for this. Where a boat stays where it rests cause no-one has the means to fetch it.
My best guess; this nice area Tanzania, Uganda, Zambia, Botswana, etc:
Just south of the equator in Africa.
That big patch is Lake Victoria - it's an overnight ferry to cross it. Lots of boats are on it.
According to Wikipedia's global warming prediction, if CO2 emissions continue to increase by 2080 this area will be 4.5 degrees warmer. These lakes are fed by melting snow on the nearby mountains, most notable being Kilimanjaro, the tallest mountain in Africa.
Mount Kilimanjaro only gets snow on it's top ~900 meters, for every 1 degree increase, this line climbs by 150 meters a 6 degree increase will stop all snow, a 5 degree increase will decrease snowfall by ~85%. If global warming in that area is 6 degrees instead of 4.5, no snowfall. No Nile flowing. No lake Victoria.
And this lush fertile land becomes desert.
250 million people rely on the Nile for water that may not exist by 2080