You can try to log out and come back in as that sometimes resets spawns. Then if you're attempting to use a raft(not a great choice though) Align your corpse icon on the map with the direction of your raft, then point your camera downward. According to some speed runners, serpents aggro is diminished from doing so.

https://www.youtube.com/watch?v=Aa6_e6GlAmE

17:00 mark.

When a serpent spawns in according to him, it will only aggro if it is in your line of sight.

So if you log out and it resets a spawn and you've pointed the camera down, the chances you get one that spawns in to aggro you is much much more limited.

As he said, it wont "de-aggro " if you catch aggro but it does seem to help from getting the aggro from line of sight stuff.

Since this guy does tons of speed runs and fully explains his strats in this and other vids, it maybe will help you to use that technique to get your stuff back.

Good luck.