When I lived in London we (coworker and I) went out and did this a couple of times, wandering the banks of the Thames at low tide and searching for whatever buried treasure the river saw fit to cough up. Nothing too interesting, a lot of china, broken pipe stems, an ancient fossil tooth (mammal, pre-ice age but not dinosaur), our finds didn't amount to much but we ran into others with better luck - one, a metal detectorist, talking to him, a bag full of shrapnel from the war, told us his best find was a 16th century widow's ring, gold, with a coffin shaped diamond...
We weren't deluded, go to the British Museum or Museum of London and you'll find that a lot of their most amazing treasures were found in the Thames, some examples below:
- https://blog.britishmuseum.org/2014/12/22/lost-and-found-toys-tears-and-the-thames/
- http://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectId=1362722&partId=1
- http://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectId=828310&partId=1
- http://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectId=65102&partId=1
- http://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectId=831341&partId=1
There's even a website devoted solely to finds on the river: http://www.thamesmuseum.org/
So to find a whole sub-niche of youtube videos that take you on the experience, well, it was inspiring...
Some articles to get you started:
And finally, here are a couple of my favorite channels:
Of course, this is a rabbit hole without end, watch the videos, there are finds of gold coins, votive offerings, abundant jewelry and pipes from all ages...
Inspiring.