The antennas for this system are used for ship to air comms, IIRC. Carriers would not normally talk to submerged subs, but MOD UK Navy do use VLF systems to talk to subs. Antenna sizes are a function of frequency and VLF systems do need long aerials.
I forgot to mention, in the picture shown, the antenna that you are talking about are vertical for normal operations and folded down, as in the picture, during flying ops. Obviously this is to not interfere with moving aircraft, both in flight and on deck.