Why Kas Specifically
Kas has some of the clearest water and most developed dive operator scene on this stretch of coast, including wreck dives and underwater visibility that the busier main resort beaches generally do not match — it is the clear answer if diving is a serious priority rather than a one-off activity.
Diving From the Main Resort Districts
Belek, Side, Kemer and Alanya all have watersports operators offering introductory dives and PADI-style courses, perfectly fine for a first-time try-dive, but not comparable in site quality to a dedicated Kas diving trip.
Other Water Sports
Jet skiing, parasailing, banana boats and similar activities are widely available at beach clubs and hotel watersports counters across every district — no need to travel for these, unlike diving specifically.
Certification Considerations
If you want to get PADI certified rather than just try an introductory dive, budget several days for the full course — this favors a Kas-based stay or a dedicated diving-focused trip extension rather than trying to fit certification around a standard resort week.
For a casual try-dive or standard watersports, any main resort district works fine; for serious diving or certification, build a Kas stay into the trip specifically — the water quality difference is real, not marketing.