Well that's where you are wrong.
This is a very cool and potentially nasty glitch. One that got my clan members and I banned from Internode for a period of time.
OK, here is what you do. Get a boat and drive to the carrier, line yourself up with the 2nd last vertical strut at the front of the carrier (pic1). Drive at it full speed and hit slightly to the rear end side of the strut. Keep the throttle on and you should begin to submerge (pic2). You will then go through the side of the carrier and be underneath it (pic3 & 4). Now here is the hard part. Put your minimap at max zoom and try place your boat in the centre of the carrier. Turn it and drive towards the back of the carrier, whilst keeping your boat icon in the centre of the carrier icon. Keep driving untill you get to where the boats spawn. Now here comes the evil part.
Make sure you are a squad leader. Stay in the boat and make sure it doesn't drift from under the carrier. Let your mates spawn on you. They can jump out and swim round, or they can go rape the carrier (pic5).
As long as you are in the boat, the enemy can not kill you, that is, unless they get their own boat and drive under the carrier as well.
The reason we were banned from internode was because we were killing swimmers with the SAW on the boat. Apparrently, that counts as camping in an uncappable flag with a vehicle.......
Our counter argument was "It's a boat for christs sake." and "Well don't jump in the friken water you idiots."
Well, there you have it. Pure evil.
Edit: Ok, my pictures are being stupid and making me angry, just deal without them.
Edit(x2): After a series of furious punches and several violent kicks aimed in the general direction of my tower, the pics are now working.











