High blood pressure. Just kidding. I'm pretty sure bunnies' heartbeats are naturally fast, faster than humans' anyway. It's probably normal. If he was scared he would exhibit other behaviours, such as running away from you, flattening his ears to his back and his body to the ground, bulge his eyes out, or start breathing extremely fast. If he's acting normal and relaxed I wouldn't worry about his heart rate too much.
As for water, how do you give it to him? In a bottle or a bowl? Bunnies tend to drink more if they have water in a bowl, because it's easier. It could also be taking him some time to master drinking from a bottle. Remember to change the water regularly too. How are his pees?
