Final answer:
The depth of the scuba diver is 57 feet below sea level, as measuring depth in this context refers to the distance from the sea level downward.
Step-by-step explanation:
The depth of the scuba diver who submerges and travels 57 feet below sea level is 57 feet. This is a straightforward reading of the depth as a measure of distance from a specific reference point, in this case, the sea level. We do not convert the measurement to meters because the question specifies the depth in feet, nor is the depth zero because we have a clear measure of how far the diver has gone below the sea level.