Baía de Sepetiba is a large coastal bay located in the state of Rio de Janeiro, Brazil, near the municipalities of Mangaratiba and Itaguaí. The bay is characterized by fast-moving tides, which can create whirlpools and overfalls, particularly near channel approaches. This dynamic tidal environment requires careful planning, as paddlers must be prepared for strong currents. The bay experiences significant commercial boat traffic due to the presence of at least three commercial docks, which is a primary safety consideration for paddlers. Vessel collisions with marine life, including small cetaceans, have been documented in the area, indicating a level of maritime activity that necessitates vigilance. Water quality in the bay has been a subject of environmental study, with reports noting elevated pollution levels. The bay offers access to idyllic anchorages and tiny villages along its shores. A specific kayaking route is documented from Ilha Bonita to Ponta da Pombeba, starting in Mangaratiba, which suggests the area is used for paddle sports. Junqueira Beach is one noted access point with views over the bay. For trip planning, paddlers should prioritize understanding the local tidal patterns to navigate the fast currents safely and be acutely aware of commercial vessel traffic when crossing channels or paddling in main areas of the bay.