San Francisco Tides

Time Event Value Units
12:21 am High Tide 6.26 ft
01:15 am Slack
05:15 am Max Ebb -4 kt
07:18 am Low Tide -0.95 ft
09:44 am Slack
12:34 pm Max Flood 3 kt
02:39 pm High Tide 4.81 ft
03:49 pm Slack
06:24 pm Max Ebb -2.1 kt
07:04 pm Low Tide 3.04 ft
09:23 pm Slack
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?