The following is from the NBC Olympics Website:

"The judges rate the execution of every dive on a scale of 1-10, including half-point margins.

Individual diving events are scored by a panel of seven* judges. Once all seven judges submit their scores for a dive, the highest two scores and lowest two scores are eliminated. The remaining three scores are added together to achieve the execution score, which is multiplied by the dive's degree of difficulty to determine the total score of the dive."

*at the high school/club/college levels, scores may be determined by a panel of 3, 5, or 7 judges depending on the scope of the specific meet.

The following information is from USA Diving. 

"Each judge scores a dive between zero and 10 points, in half-point increments.

Scores are defined as follows:
10: Excellent
8½-9½: Very good
7-8: Good
5-6½: Satisfactory
2½-4½: Deficient
½-2: Unsatisfactory
0: Completely failed

Judges evaluate the following parts of a dive to determine an overall score:

Approach: Three or more steps forward to the end of the board before the hurdle and takeoff. Should be smooth but forceful, showing good form.

Takeoff: A diver’s lift from the board prior to execution of the dive. Must show control and balance, plus the proper angle of landing and leaving for the particular dive being attempted.

Elevation: The amount of spring or lift a diver receives from the takeoff greatly affects the appearance of the dive. Since more height means more time, a higher dive generally affords greater accuracy and smoothness of movement.

Execution: The dive itself. Form: A judge watches for proper mechanical performance, technique, form, and grace.

Entry: The entry into the water is significant because it’s the last thing the judge sees. Judges favor a graceful, vertical entry along with a minimal amount of splash.

While it takes seven judges to score individual competitions, 11 judges score synchro events. During a synchro dive, three judges score the execution of Diver A’s performance, while three other judges score the execution of Diver B’s performance. The remaining five judges score the synchronization of the pair.

A diver’s overall score for an individual dive is calculated in the following way:

1. Each of the seven judges awards a score to a diver for his or her dive. (Ex: 6-5-5-5-5-5-4)
2. The two highest and two lowest scores are eliminated. (Ex: 6 and 4 and two of the 5s are eliminated.
3. The remaining scores are totaled. (Ex: 5 + 5 + 5 = 15)
4. This total (15) is then multiplied by the predetermined degree of difficulty rating associated with the particular dive performed to calculate the overall score. These degree of difficulty ratings range from 1.2 to 4.1, in one-tenth increments. (Ex: 15 × 2.0 = 30)

For synchronized diving, a score for a dive is calculated in the following way:

1. Three judges score the execution of diver one (Ex: 6-8-7); three judges score the execution of diver two (Ex: 9-7-8); five judges score the synchronization (Ex: 7.5-8-8-8-8.5)
2. The highest and lowest execution scores for each diver are eliminated, as are the highest and lowest synchronization scores. (Ex: 6 and 8 for diver one, 7 and 9 for diver two and 7.5 and 8.5 for synchronization are eliminated.)
3. The remaining scores are totaled. (Ex: 7 + 8 + 8 + 8 + 8 = 39)
4. This total (39) is then multiplied by the predetermined degree of difficulty rating associated with the particular dive performed to calculate the overall score. These degree of difficulty ratings range from 1.2 to 4.1, in one-tenth increments. (Ex: 39 × 3.0 = 117)
5. Finally, this total (117) is multiplied by 0.6 to calculate the overall score. (Ex: 111 × 0.6 = 70.2 overall points). "