Answer:
57%
Step-by-step explanation:
You need to find the percentage of people that are either on the boardwalk or the sand. Do this by adding the two given percentages.
20% + 23% = 43%
Since the rest of the people are in the water, you can subtract the percentage found above (43%) by 100% to find the answer.
100% - 43% = 57%
The percentage of people in the water are 57%