Koos, you will only require one antenna for both the 29MHz Marine Channels as well as the 29MHz 4x4 channels. You would not normally require the 27MHz CB channels at all, very few people are using it.
The radio could be programmed for the three Marine channels as well as the three 4x4 frequencies, no problem.
White Fang: 1999 2.7i DC Raider 4x4
Bull Dog: 1987 4Y-EFI 2.2 DC 4x4
Pra Dog: 1998 Prado VX 3.4
Hound Dog: 2000 2.7i SC 4x4
One Staffie, One Jack Russell, One Ring Neck Screecher, One Gold Fish