Back in the day, tables were the only option. Now, the majority of scuba divers wear a wrist-mount computer and for good reason.
The computer monitors depth, bottom time, ascent rate, and no-decompression limits in real time. Dive tables are a fixed calculation. If you move between depths mid-dive, it updates. A table can't.
Wrist computers are what most people buy at this point. These are small enough, readable underwater, and you'll use them as a daily watch as well. Hose-mounted models are available but less buyers choose them these days.
Entry-level computers start around a few hundred dollars and handle everything the average diver would need. They give you depth tracking, bottom time, no-deco limits, dive logging, and usually a simple freedive function. Stepping up to mid-range adds air integration, better readability, and extra gas modes.
Something new divers don't think about is algorithm differences. Some computers are more conservative than others. A cautious setting results in shorter bottom time. Looser settings extend bottom time but with less safety margin. Neither is wrong. It just what you're comfortable with and your diving background.
Check with someone at a local dive store who uses a few different computers first. They'll best dive computers have honest opinions on which ones hold up versus what's just marketing. Decent dive shops publish gear reviews and comparisons on their sites as well