Hatchling terrapin

Bought a new diamondback terrapin, it is acting very strange. It stays only at the top of the water, sometimes sinks a bit, and then swims back up. It does not show any fear and is not feeding. Swimming frantically all around against walls of tank, has been for hours.

Are you keeping it in freshwater or brackish?

I am keeping it in brackish, I would like to add, the turtle's armpits for lack of a better word appear to be swollen. He also is at the surface and swims as though he is drowning, he cannot easily get under objects and appears to little control over his buoyancy. I placed him on his basking platform and he is basking, but couldn't figure out how to do it himself

salinity is 1.005, it is a concentric northern for further information

Your basking platform might be too high for him to reach comfortably. I'm no expert but if you post photos of the tank and the terrapin I'm sure someone on here could help.

It is not too high, he can easily access it, I will post a picture. He started to react more to stimuli, albeit slowly.

I took a bunch of photos but I cannot send them because the website is asking for links to photos and I have none

This may help:

https://www.faunaclassifieds.com/for...d.php?t=304671

heres the photos