Game Mechanics: Casting on Iron Guardians/Sentinels in OT

[Bikamin]

This is in the Over There, when Iron Guardians/Sentinels run into the water I cannot cast on them, I have tried being in the water next to them, levd over the water, or on the surface of the water, I always get the you cannot see your target. While they are in the water it appears like they are still running like they are still on land.