GUESS who was out hunting for sharks at the weekend? (By that we don't mean he was seen alone and unprotected diving into the Hongkong Press Club.) It was none other than Star TV's toughie VP ''Colonel'' Arnie Tucker. Our spies tell us he was operating off the costal waters looking for Jaws of Sai Kung. Arnie, who based his unsponsored misson to rid our waters of this predator of the deep from a luxury yacht with a fully-equipped bar (essential prerequisites for this type of perilous work, he was heard to claim) pointed out that his strategy was simple:''If it bites me, I just bite back.'' And anyone who has had a close sighting of Arnie's fangs know this was no idle threat. He added: ''The secret is you have to be able to swim with the sharks to survive.'' As a long-standing media and marketing man, Arnie knows what he's talking about.