Which was exactly the same situation as in 2010 when I visited AQWA. I thought their labelling was generally pretty poor - obviously nothing's changed. The specimen exhibited in 2010 was a Shark Bay Sea Snake (Aipysurus pooleorum): the one in this photo could also be that taxon.
Apparently this is a Shark Bay sea snake, and is very likely to be the same specimen which Mike saw (and maybe even LaughingDove), which would be very impressive.