The tank measures 160mm (length) x 90mm (width) x 45mm (depth). The device is really good (I use it to clean my glasses).

without basket fits your gopro. 90x160x45... 45 is the filling height, at most it could be that it is not completely covered with water and needs to be turned over.

I wouldn't put a gopro in this device. It's not recommended for watches either. Just let it soak in soapy water and the salt comes off.