I am a search and recovery diver. Hence, my list is a bit long. I could have picked one or two items only, but it is fun to share, so...
I've found a few interesting things, indeed. I live in a city that was formed in the 13th century and it has a river flowing through it. On one of my dives I stumbled upon an ancient mill stone (it's quite rough, though???). Another guy located an admiralty anchor that I helped to haul along the bottom so that it could be reached by the crane (no sufficiently large lifgt bags nor the verticality to use such).
Pics in this article (in Finnish):
Romunsukeltajat törmäsivät yllätyslöytöön Aurajoessa
This was the most memorable find. As a close second will come a moped/scooter/something:
Vapaaehtoiset sukeltajat nostivat moposkootterin Aurajoesta – sukeltaja: "Ehkä voisi jättää heittämättä"
and then there have been other things:
- a hand-pump pallet jack truck,
- a large metal shopping cart with four wheels,
- a cast iron bench - someone unknown to me apparently filmed it (and it was a hell to dig it up from the bottom sediment with hands and a crowbar):
),
- traffic signs,
- stretchers from an ambulance boat,
- a whistle, made out of clay, formed as a rooster,
- an abandoned fyke net flat on the bottom
Bicycles and electric scooters are too numerous to count.
(that dive was pre-covid).
