Bakau's botanical gardens are small and not particularly well maintained, but that is not entirely a drawback. The shade is dense, the paths are quiet, and the trees attract a good range of birds. For anyone with binoculars and patience, an hour here in the early morning can turn up sunbirds, weavers, and various raptors overhead.
Entry is cheap. Go early for birds; go in the afternoon for shade and quiet if you need a break from the coast.