Costa Rica: It comes with the territory.
Playa Grande really is as rugged and raw as you'd imagine. Be mindful, go prepared, and respect the elements.
1. Stay hydrated. Not only is the beach warm, but the ocean temperature stays in the 80's year round. Unfortunately, the tap water there is not potable. Bring a light pen to zap the bacteria before drinking or pack water tablets. You can also buy bottled water at the store but I recommend saving your money for the "pipas frías" (cold coconuts) the locals sell on the beach.
2. Pay the 500 colones. It only cost $1 to cross the river to Tamarindo by boat. DO NOT SWIM OR PADDLE ACROSS. There are crocodiles who live there that have been known to attack trespassers. A good rule of thumb in Costa Rica: Do as the locals do and you'll be good to go.
4. Take a first-aid kit with you. There's really only 1 tiny store in Playa Grande, Wil Mart (haha!). If you're accident prone like me, bring a small kit with Band-aids, Antiseptic, Gauze, Tape, and Liquid Skin. Hopefully you won't need it but I just about used all of mine...oops.
5. The bichos can be a bitch. Like any tropical paradise, there are bugs...namely mosquitos. Repellent really does help but in case you still get bit, Tea Tree Oil works wonders to not only soothe the irritation but to help them go down quick! They like sweaty, wet bodies but can be deflected by loose clothing like beach pants and lightweight long sleeves. It took me a very long time to figure all this out on my own. Please, go prepared!