If he jumps in the water when you walk by, it would be good to put a barrier around the outside of the tank where he basks so he can't see you.
What's the temp of the water and basking area? A basking area temp in the range of 88 - 90F is good (high 90's is too warm). There should be about a 10-degree difference between the water and basking area (so figure no more than 78F) to encourage him to bask for the warmth.
