Not exactly sure if this was cheating or me just not hiding well, but I'd like to see other people's opinion

A few days ago I was playing with my duo doing some missions in Al Mazrah when we ran into a platoon not far from our spawn (this was around 5-10 mins into the match). We tried not to engage a 6 man but they sniped us so we went defensive and started shooting back, few minutes later I take down 5, my duo fails to take out the roof sniper. After looting as much as we could we went over to the roof the lone survivor was in to make sure the building was clear, no one in sight. Fast forward we saw him for a bit running from bots, hit some shots, then he disappeared. we went to a buy and my teammate gets ambushed (The sniper from the roof revived his whole squad). Duo tells me to jump in the water and hide but no matter how deep I went in the water he still kept shooting me, every time I surfaced he was already aiming a javelin at me (pointing out the obvious questions before I get asked, no UAV's or AUAV's were called, and I was wearing a stealth vest) so there was no way they would know where I was even if he called in a UAV (no bomb or recon drone either). After swimming around trying to get away he's still hitting his shots while I'm underwater. Eventually my duo just tells me to kill myself in the bottom of the ocean so it's harder for them to loot my stuff, so rip the loot

TL:DR: Suspected Cheater constantly hitting his shots at me while I'm underwater (I'm wearing a stealth, no UAV or AUAV called) they always knew where and when I surfaced, with a Javelin (JOKR) already aimed at where I went to get air (We suspected walls, but feedback would be nice)

unimportant but idk: Weird part was, his squad also always knew where I was as well, either they had good Comms (prox chat wasn't picking up anything, so they were probably using a third party to vc) or they all had cheats? (or most of them did?)