Between these bays there are extensive stands of mangroves in the mouths of the San Juan, Naya, Guapi, Mira and Esmeraldas rivers.

[1][a] In the northern section the continental shelf is narrow, with the land rising steeply from the shore to around 1,500 metres (4,900 ft) above sea level.

[1] The mangrove forest strips run parallel to the coast in the southern section and may extend inland for as much as 20 kilometres (12 mi) due to the 4 metres (13 ft) tides.

[7] Depending on the local topography and climate, mangrove formations include bar, inverse estuary, coastal, dwarf, border and small island.

[2] Compared to the Caribbean, the Pacific mangroves of Colombia have lower salinity due to the high rainfall and tidal action, and their zoning may be more dependent on stability of the substrate.

The abundant nutrient-rich fresh water results in exuberant growth, with heights over 40 metres (130 ft), and high production of organic detritus.

[1] Common plants include Amphitecna Gentry, black calabash (Amphitecna latifolia), Crenea patentinervis, açaí palm (Euterpe oleracea), coast cottonwood (Hibiscus tiliaceus), Lonchocarpus monilis, Mora oleifera, Pavonia rhizophorae, Phryganocydia phellosperma, mangle marica (Tabebuia palustris), Tuberostylis axillaris and Tuberostylis rhizophorae.

Sandy areas have field sandbur (Cenchrus pauciflorus), Homolepis aturensis, and climbers such as beach bean (Canavalia rosea), bayhops (Ipomoea pes-caprae), fiddle-leaf morning glory (Ipomea stolonifera), Pectis arenaria and St. Augustine grass (Stenotaphrum secundatum).

[6] Bromeliaceae and Orchidaceae epiphytes that invade the canopy include Vrissia grandioliflora, Guzmania musaica and Heliconia bihai.

[10] Common bivalves include Anomia fidenas, Gould's shipworm (Bankia gouldi), pleasure oyster (Crassostrea corteziensis), thin purse-oyster (Isognomon janus), striate piddock (Martesia striata) and brown falsejingle (Pododesmus foliatus).

Common crustaceans include grapsid crab (Armases angustum), Callodes gibbosus, Eurypanopeus transversus, Eurytium tristani, Glyptograpsus impressus, Latreutes antiborealis, Macrocoeloma villosum, Notolopas lamellatus, Panopeus chilensis, Panopeus purpureus, Pinnotheres angelicus, Cangrejo de pantano (Sesarma aequatoriale), Sholometopus occidentalis and Sholometopus rhizophorae.