The Río Sierpe (“Sierpe” means “serpentine”) is tidal for its entire length with the village of Sierpe being the dividing line between fresh and brackish/salt water. Above (east) of Sierpe is fresh water, immediately to west is brackish, and further west (down river) is salt water. Regardless of tides, the river channel is a minimum of four meters. Thus, boats can pass the river at any time, not only in mornings.

The river contains many types of fresh and salt water first; snapper (several species) predominate, corvina (corvina is not in the same family of fish as sea bass –regardless of restaurant menus in San José), grouper, snook, and many other species.  

The mangroves adjacent to river and in the Sierpe Delta are nurseries for wide variety of marine life; shrimp, clams, fish, crabs, snails, etc. All thrive in the protected mangrove waters (the several species of mangroves are only in salt or brackish water-never in fresh water). The crocodiles are fresh water crocodiles, but they will feed in salt water, particularly on mullet that literally swim in front of the crocodiles.

At the point where the Rio Sierpe enters the Pacific, the mouth or “boca” is quite narrow and the currents and waves can be impressive.

These are several factors, which influence the “roughness” of the Boca:

  • Higher tide levels generally dampen wave size- the higher the water level, the smaller the waves.
  • The new and full moons are significantly larger and with faster currents than the other lunar phases. For example, a new moon tide could have a high water mark of more than three meters above mean sea level, while the low mark could be below the mean sea level. Currents during this time will average 12 km per hour and waves at the Boca particularly during low tide could be substantial.
  • The wind affect the intensity of the Boca by impacting the angle and size of waves as well as introducing “chop” to water (particularly in afternoons).

The relatives “smoothness” of the Boca is determined by these factors which vary daily and over monthly cycles - the time of day has almost nothing to do with the smoothness or roughness of Boca. Also the currently used boats and motors have very little similarity to the boats and motors of 25 years ago.


Much of the coastline is “open” and is subject to the same influences as Boca Sierpe.

Exceptions include Drake Bay where boats can enter a river to embark / disembark; Caño Island where entry to the ranger station is protected by large surface rocks and Playa San Josecito which has a ring of protective rocks. Both Caño Island and San Josecito have “wet landings”, sandals should be worn instead of shoes. Also landing can be rough on occasion when winds are coming out of specific directions. Entry and landing at San Pedrillo or Sirena in Corcovado Park, are generally a higher level of “roughness”.



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