Good stuff Andrew. I worked on pools as a summer job in 1955-1957 built in Florida, several within 100' of the Gulf of Mexico using the same method: for a 10' deep pool, dig as small a hole to approx 12-14' deep followed by a bucket load of gravel, a ribbed 4" suction hose and pump sucion head. This kept the pool and groundwater under control during construction of reinforced form cast and gunite concrete shells). The hose and pump head ended up being under the pool and tied back to a an access box in the pool deck. This hose is used for future pool jobs (plastering, painting, etc) to lower groundwater to empty the pool without fear of floating the pool.

I spy some Danella swag

You need a smooth bucket.