Ubatuba is strongest when you split your time between sea and forest. The central waterfront has the aquarium, Projeto Tamar, restaurants, and boat offices, but the real reason to come is the long coast north and south of town. Surf beaches, calm family beaches, waterfalls, rainforest trails, and the offshore Ilha Anchieta all fit within a day if you choose one area instead of trying to cover the whole municipality.
For a first visit, pair one beach with one nature stop. Itamambuca is the obvious surf choice, Praia da Fazenda is better for a quieter protected landscape, and Ilha Anchieta is the most complete outing if you want beaches, snorkelling, and history in one boat trip.