Bug or super secret ocean treasure?

[SpeedyBullet]

So I defeated one of the cultist who was on a boat far in the ocean bottom left of the map. After defeating the ship and thus kiling the cultist I noticed 2 chests on the ocean floor while using Ikaros. I tried swimming down to see what's going on down there but it's so deep that I always end up drowning! D: I know there is an engraving that you can breathe underwater but I did not unlock this engraving yet. Anyone know what is down there?

Maybe it's just a bug and nothing more but it has certainly spiked my curiousity :o

Screenshots:

https://imgur.com/RxAqlKa

https://imgur.com/cJCBsmO

https://imgur.com/qrjnQOn

Update: I swam down there using second wind to heal from drowning and there was a chest! The contents however were very dissapointing.... https://i.imgur.com/0fOcfMb.jpg

I wanted to go back there to find out what was in the second chest but I can't find it anymore despite having it marked before :c

[Fallen]

the chests likely belong to the cultist ship, if you cleaved the ship the chests sink down and can be opened if you are either quick enough to get them as they are going down or if you have the engraving. Nothing really special inside of them other than the usual stuff, i came across a bug that if you are close enough to land and cleave a cultist ship and the cultist somehow survives but you still get credit you can get 2 of their legendary item if you jump in and kill them as they swim.

[SpeedyBullet]

Yea you are right I did cleave the cultist ship so it's just the loot from the ship that sank down. Mystery solved I guess!

[Hollywood]

Yeah keep that in mind when you cleave elite ships on accident, the loots still down there. Also the engraving for breathing underwater is easily found on the far east between Chios and Samos if you want to pick it up quickly.