Travelers to Costa Rica need a travel visa, a passport that isn't nearing expiry and proof of a return ticket. Airlines restrict what can and cannot be taken in and out of the country. Different airlines have different rules, so check with your airport before embarking.
Knowing the Costa Rican laws and regulations also helps. All types of drugs are illegal, so make sure that, if you're on prescription drugs, you carry your prescription with you all the time.
Also, beware of pickpockets. Tourists are favorite targets, so keep your money safe and as close to your body as possible. Don't carry more money than you need and carry smaller denominations.
As for clothes, though Costa Rica is known for its beaches and hot summers, the weather is cooler on the higher planes and at night. Nudity on beaches is illegal, but there are a few secluded nudist beaches like Manuel Antonio.
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