In the Story mode, the Deep Divers act differently than in Mapmaker. They move as if they cannot lift their legs, use their Harpoon Guns with one hand and cannot be killed with a single headshot from any type of pistol. This is likely a reflection upon the weight of their suits that they wear. However, they retain normal human flinch/death animations.
If one chooses to play as the Deep Diver, they will see him holding the weapons with his bare hands, much like Ivor Baddic and most other characters from Kronia, instead of wearing his gloves. This was likely an error or an oversight.
As a Story AI, he can't see as far as every other AI. Also there is no animation for his Story AI to dual-wield, resulting in an inability to aim if he is equipped with any 2x guns. This inability to dual aim is suddenly rectified once the player turns his back on him, an example of the many Line of Sight Glitches in the TimeSplitters Future Perfect Mapmaker.
Despite exclusively using the Harpoon Gun in TSFP's Story, the Deep Diver seems to pump his weapon after every shot in the Mapmaker. This may mean that they were originally supposed to wield Tactical 12-Gauges (likely brought over by Henchmen who time-travelled from 1969), as no pump system exists on the Harpoon Gun. This also means that the Diver holds every weapon like the 12-Gauge, which may be the cause of him being unable to shoot dual-wielded weapons.