Years ago, dive tables were how everyone dived. These days, nearly all divers use a personal dive computer and for good reason.
Your computer calculates depth, time, speed of ascent, and no-decompression limits in real time. Tables can't do that. When you move between depths partway through, it updates. find out here Tables don't.
Wrist computers are the most common buy now. They're compact, readable underwater, and you'll use them as a daily watch between dives. Hose-mounted models are available but less divers pick them now.
Budget computers start around $250-400 and handle everything the average diver requires. You get depth tracking, time, NDL, log function, and sometimes a basic freedive function. Stepping up to mid-range includes transmitter compatibility, improved screens, and extra nitrox compatibility.
Something new divers overlook is conservatism settings. Some computers are more conservative than others. A conservative computer gives you shorter NDL. Liberal algorithms allow longer time but with less buffer. Both work. It just your style and your diving background.
Worth talking to someone at a Cairns dive shop who dives with various brands before you decide. Staff will have a straight answer on which ones hold up and what's hype. Most good dive stores put out buying guides and honest reviews on their sites as well