The deep ocean channel immediately south of Mauritius is one of the most reliable whale watching destinations in the Indian Ocean. Between June and October, humpback whales pass through on their annual migration between Antarctic feeding grounds and tropical breeding waters, and sperm whales are resident in the deep channel throughout the year.

Trips depart from Le Morne on the south-west coast and head south into deep water — the continental shelf drops away rapidly here, reaching depths of over 1,000 metres within a few kilometres of the shore. The humpback whale season peaks in August and September when the whales are most numerous and active. Sperm whales are encountered year-round in the deep channel, though sightings are less predictable.

The south coast boat operators are among the most experienced whale watching guides in the Indian Ocean. Crews use hydrophones to listen for whale calls and spotter boats to extend the search area, which means sighting rates are high by regional standards. Humpback whale behaviours seen on these trips include breaching, fluke-up dives, and pectoral fin slapping — all at close range. The operators hold permits from the Mauritius Fisheries Division that regulate minimum approach distances.

Trips typically run 5–6 hours, departing early morning. Rough sea conditions can affect departures; the south coast is more exposed than the lagoon-protected north and east coasts, and trips are sometimes cancelled or postponed. All reputable operators offer a credit system for cancelled trips due to weather. Bring sea-sickness medication if you're susceptible and dress in layers — the ocean south of Mauritius is noticeably cooler than the beaches.