The strait is unusually deep, 250 m. That seems quite a slope.
Apparently we already have underwater tunnels 292 meters below sea level https://en.wikipedia.org/wiki/Ryfylke_Tunnel#:~:text=The%20R...
It's also a question of length though. If you go down 292 m and then back up over 14.4 km, that is a 4% slope on average. But to go down 250 m and then back up over 3.3 km, it requires a 15% average slope.
I mean both Sicily and mainland Italy have more than 7km of land on either side to ascend into.
Apparently we already have underwater tunnels 292 meters below sea level https://en.wikipedia.org/wiki/Ryfylke_Tunnel#:~:text=The%20R...
It's also a question of length though. If you go down 292 m and then back up over 14.4 km, that is a 4% slope on average. But to go down 250 m and then back up over 3.3 km, it requires a 15% average slope.
I mean both Sicily and mainland Italy have more than 7km of land on either side to ascend into.