San Francisco Tides

Time Event Value Units
01:00 am Slack
03:16 am Max Flood 0.9 kt
04:00 am High Tide 4.82 ft
04:51 am Slack
09:11 am Max Ebb -3 kt
11:08 am Low Tide -0.31 ft
01:48 pm Slack
04:43 pm Max Flood 2.2 kt
06:51 pm High Tide 4.51 ft
08:04 pm Slack
10:51 pm Max Ebb -1.7 kt
11:57 pm Low Tide 2.93 ft
What day is the longest?
Why are there 2 tides per day?
Why doesn't Slack = High/Low Tide?
Why can you ride a flood but not an ebb?