Haily, it does not matter if you water the crops or not, they will come back at their scheduled time. So if you need food, by all means don't let them water the crop, get them foraging.
As far as the time it takes to finish the patch and lagoon, it does take some time. If you click next to the blockage you should see what % has been cleared. The patch on the other hand has not completion "meter", so you just have to keep going.
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The VI