The water track
Dolphins, resident year-round
Not a seasonal migration you have to time your trip around — common and bottlenose dolphins live in the bay permanently, which is why most cruises mention them as a realistic expectation rather than a marketing promise.
What you'll actually see
Pods of common dolphins are the more frequent sighting; bottlenose dolphins are also present but in smaller, more localised groups. Sightings happen across the bay, including on the standard Hole in the Rock route — it isn't a separate specialist trip you have to book instead of the main cruise.
Swim-with-dolphins trips
Some operators offer in-water encounters, regulated to protect the animals — swims are called off if a pod includes calves, or if the dolphins show disinterest. Treat any swim trip as a possibility, not a guarantee, on any given day.
Where this fits
Dolphin activity is a bonus on most water-track trips rather than a separate line item — factor it into the Hole in the Rock cruise or an island-hopping day rather than budgeting it as its own day.