There are many places where whales, dolphins, whale sharks, stingrays etc. can be seen by a guided boat tour, a snorkel trip or even from the costal line.
The dry season in the Yucatan runs from November until April. Since Sian Ka'an is only reachable by quite a rough road it is not advised to visit in the wet season, especially if you DIY.
Migration of Humpback Whales from mid-December through mid-April. The peak time for this whales and most mating activity last from late December to January.
Many whales and dolphins are year round at the Canary Islands. Best weather from April to October, shoulder season April-June and September-October are less hot and crowded.
Sea Lion colony, doubles in size in summer, pupping early July, mating a couple of weeks later.
From June to November Southern Right Whales visit the shore, and it is one of the most important nurseries from July to October.
The southern right whales migrate to the coast of South Africa from Antartica during winter and spring. They come to the warmer waters for mating, giving birth in protected lagoons, and feeding. They arrive in June and July and stay until November latest December before migrating back to the colder waters of Antartica. These whales can be spotted in De Hoop, Hermanus and along the Garden Route like in Mosselbay.
This coastal walk from Gansbaai is not much frequented rather still off the beaten track. Here you are able to spot these majestic giants close to the shore while hiking. The return hike is roughly 10 km long and may take 3-4 hours from Gansbaai to De Kelders and to the Klipgat Caves. The caves are accessible at low tide only. Check the tide times first: Tide Times Gansbaai