Haydee is capable of basic horizontal movement while swimming above water; being able to move forwards in any direction and grab sufficiently low ledges above her.
However, Haydee is also able to submerge herself in water for vertical movement as well. This allows Haydee to reach the bottom of pools and swim under obstacles that would otherwise block her path. However, Haydee can only spend 20 seconds underwater before beginning to drown and take damage; even when starting off at full health, Haydee is guaranteed to die after a total of 30 seconds.
Additionally, almost all actions cannot be completed while swimming; items that trigger specific animations, including shooting/reloading firearms, deploying mines and using the Remote Control are completely impossible. However, instantaneous actions such as equipping Wearables, using Medkits and placing Remote Devices are unaffected. Additionally, manual inventory reloads, dragging ammo onto a weapon, can be done as well.