Sven likes to water ski, but can only water ski during the one week each year when he is on vacation. Therefore, he plans to ski every day, for eight hours a day. The first day, Sven skied for eight hours and enjoyed every hour. The second day, Sven slept in and then skied for seven hours, which was fun but not as much fun as the first day. The third day, Sven skied for six hours, but was starting to get a bit bored by the end. The fourth day, Sven skied for four hours and then took a nap. On the fifth day of Sven's vacation, Sven went blueberry picking all day. Sven's total utility with each hour that he skied.

Sven's total utility INCREASED, BUT EVERY TIME IT INCREASES A LITTLE BIT LESS with each hour that he skied.

Explanation:

The law of diminishing utility can explain what happened to Sven, since the more you consume of a good or service (water skiing), the marginal utility that you obtain from that consumption will decrease.  

E.g. imagine that you are extremely thirsty and you decide to drink a Coke. Since you were very thirty, the Coke that you just drank gives you a very large amount of utility. But then you decide to drink another Coke because it is really hot outside. This time the second Coke was good, but didn't provide that same utility as before, even though it still felt good. Since you really like Coke, then you decide to have a third one, but this time you barely enjoy it and don't even finish it.  

answer; sensory adaptation;