@new tip People it can attack you in water...

That is then if you are right in its face. Use an amphibian or a mount that doesn’t need oxygen when swimming (baryonyx is good, Beelzebufo is good to, whichever you choose, my personal fav is the frog) and is fast. Kite behind the arthro if you wanna tame it, ghillie or bug repellant is optional though. If you need to kill it, then use guns (preferably longnecks or high quality snipers, things that can one shot one kill) either to the face or just shoot it. Arthros have a 3x damage multiplier to guns, and a 4.5x headshot multiplier. Or use explosives. They have a 5x damage multiplier to them. Use spygalsses to check levels.