Well, I got hold of a high speed USB Dongle which I could connect to my laptop/desktop. But I couldn't use it's internet with Aqua Fish. So I thought I would try to share the internet and see how it works out.
1. Make laptop WiFi hotspot - normally it's effortless with apps like Conenctify,but on this current laptop I don't have admin access. Which means I can't do this using windows. But I have Linux on this too. So I rebooted and googled about WiFi hotspot on Linux. Got some decent instructions too. But it wasn't working. So after changing the WiFi driver twice, following three different tutorials, and finally finding out that this laptop's WiFi doesn't have any driver that supports AP functionality, I was disappointed.
2. Try USB Reverse tether on Jolla: The instructions were there. But people threw a number of disclaimers so I thought my phone's brand new. Don't wanna break it so early. Which means this was also a no no.
3. Try USB tether on android and make it WiFi hot spot: Well, getting reverse tether to work was an experience in frustration. Mainly because somewhere between android 5.0 and 6.0, they changed a number of networking commands and thus invalidating all those simple 3-4 command tutorials.
Finally after trawling the web for couple of hours I found what one lucky soul had posted regarding Android 6.0. I followed that tutorial but somewhere between 7th or 9th command I got lost.
Not so easily giving up, I found another option: An App in Play Store called Reverse Tethering NoRoot Free. Following their instructions I installed companion app on desktop. And fired it all up. I did get reverse tether working with this. But when I tried to turn on WiFi hot spot so that I could share this hard earned internetz to Aqua Fish, it just wouldn't work.
Well, they say third time's the charm. For me three tries are more than enough.
Summary: I changed laptop WiFi Linux drivers thrice. Trawled internet for more than four hours. Installed Linux ADB Driver. Fired about 4 dozen commands in ADB Shell. Fired twice that commands in terminal. And managed to get Android Reverse Tethering working with a ready-made app from play store.
Some days are just so bleak...