Sun is very potent, even on cloudy days. Use sunscreen. Also you can snorkel or swim in a T-shirt.
Humidity is very high. Protect your electronic equipment by bringing water proof bags and moisture absorbent packs.
Some of the food on the street might contain hard particles. Take care when you chew. It's not the case with good restaurants.
The ice is safe. The water not always. Drink bottled water.
Goods are cheap in Bali. Don't bring too much unnecessary stuff.
Make sure you bring medication. Including cold and stomach medication.
Balinese food can be very spicy. Sample it with caution.
