How to get the Megagong without hours of obnoxious grinding due to awful RNG.
Getting the Gong
This will save you a ridiculous amount of hours of obnoxious grinding time due to poorly designed RNG.
Complete the game like normal. At the end you need to make about 30 fish holes in each zone close to your base. The more the better. You should be able to make quite a bit just from leftover resources. The bombs hit in a 3x3 pattern so try and stay close to that formation. Grind out 10 or so fish magnets/fish bombs for each zone. Save. I'm guessing having the Epic Guliani helps but I'm not 100% sure. I had it with me but I did not have the fish idol passive. Now go offline on your friends list so you're not annoying your friends with constant steam updates. =]. Alright. Here's the process:
Exit house...bomb until most the holes are completed. Is there a Gong? Yes? Hit Pause/Escape (this automatically saves your inventory.) Move onto next zone.
No gong? DON'T HIT PAUSE. It is important you do not hit pause or escape. When you hit pause/escape it saves your inventory/bomb count. By not doing this you won't have to grind obnoxiously for the ingrediants needed to make the fishing bombs. After NOT HITTING PAUSE you will Cntrl + Alt + Del >Crashlands > End Task > Reload your game. You will spawn with original amount of bombs from when started originally and all fish spots replenished. Repeat. Took me an hour of just doing this to get Bawg + Tundra gong. I'm not sure how often the game autosaves but you may want to bomb the farms and assess the drops as quick as possible. I was taking my time to be honest and never really had a problem. May want to back up your save cause I could see it getting corrupted this way.
Afterwards grind out the ingrediants needed for the lure and do a little fishing. It did not take me long to get the actual weapon from fishing. I did a little in Savannah but ended up finally getting it in the Tundra. Not sure if that matters.