Game freezing entire PC in sharkwing tilesets.

[-NW-Darkcloud]

Hello and to the point.I don't usually play underwater archwing missions but sometimes i have to , like in the sorties.The thing is that when i go underwater my PC is just frozen sound ingame is bugged and i can't do nothing.Checked in task manager how's mine performance and it was 13% usage of processor and 2Gb memory used.Im using six-core processor(3,5 GhZ) + Nvidia GeForce GTX 970 also 16Gb RAM memory so i have totally not a clue what's happening.