San Francisco Tides

Time Event Value Units
01:36 am Max Ebb -2.3 kt
02:56 am Low Tide 2.21 ft
05:06 am Slack
07:06 am Max Flood 1.2 kt
08:29 am High Tide 4.46 ft
09:36 am Slack
01:36 pm Max Ebb -2.8 kt
03:04 pm Low Tide 0.35 ft
05:30 pm Slack
08:12 pm Max Flood 2.3 kt
10:05 pm High Tide 4.86 ft
11:12 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?