Costa Rica is a largely safe country, but petty crime (bag snatchings, car break-ins etc) is common and muggings do occur, so it’s important to be vigilant.
Costa Rica lies on the edge of active tectonic plates, so it is decidedly earthquake prone. Recent major quakes occurred in 1990 (7.1 on the Richter scale), 1991 (7.4) and 2012 (7.6). Smaller quakes and tremors happen quite often (one area that sees particularly frequent seismic activity is the Península de Nicoya), cracking roads and knocking down telephone lines.
Two of the most popular volcanoes in Costa Rica, Poás and Turrialba, have been very active recently with a number of eruptions of varying degrees since 2014 and 2015. Due to safety concerns, the national parks surrounding these protected sites were closed at the time of research. Check the status of each before you visit.
Hikers setting out into the wilderness should be adequately prepared.
Each year Costa Rican waters see more than 100 drownings, the majority of which are caused by riptides (strong currents that pull the swimmer in different directions). Many deaths due to riptides are caused by panicked swimmers struggling to the point of exhaustion. If you are caught in a riptide, do not struggle. Swim parallel to shore; eventually the riptide will dissipate. Alternatively, you can float until the riptide dissipates, then swim parallel to shore and back in where there is no riptide.
The biggest danger that most travelers face is theft, primarily from pickpockets, but also when personal possessions are left in parked cars. There is a lot of petty crime in Costa Rica, so keep an eye on your belongings and your surroundings at all times.
The following government websites offer travel advisories and information on current hot spots.
Australian Department of Foreign Affairs (www.smarttraveller.gov.au)
British Foreign Office (www.gov.uk/foreign-travel-advice)
Canadian Department of Foreign Affairs (www.dfait-maeci.gc.ca)
Dutch government (www.nederlandwereldwijd.nl)
German Federal Foreign Office (www.auswaertiges-amt.de/de)
Japanese Ministry of Foreign Affairs (www.anzen.mofa.go.jp)
New Zealand government (www.safetravel.govt.nz)
US State Department (http://travel.state.gov)