I had the unfortunate experience last week of eating some raw oysters on the Malecon in Puerto Plata. I was sick for two days straight. Afterwards, I was warned that you should never eat shellfish that vendors sell on the beach (i.e. oysters, shrimp, etc.) or walking around in town as they walk around with their goods all day in the hot sun and whatever they don't sell they go home, put it in the fridge overnight and bring it out the next day. To those travellers who may be tempted to indulge in the local food on the beach, please save yourself the agony and misfortune of spending part of your holiday in bed.