In last nights episode we saw a symbol in the bunker, went looking for a picture but didn't find one yet, it if I remember correctly had a wave in the middle which was surrounded by three hexagonal (one inside the other, etc) and each side of the hexagonals was made of one or two pieces which looked a bit like long and short dashes, morse code maybe? If so that each side is a number, abet only a single digit number.

But what really caught my attention about the symbol was that it was tattooed on to the shark that was stalking the two lads on the raft - yeah for TiVo and 8 second rewind.