Your first dive is to 60 feet for 50 minutes, and you spend one hour and 40 minutes on the surface. What is your adjusted maximum dive time at 60 feet?

To determine the adjusted maximum dive time at 60 feet, it's essential to consider both the depth of the dive and the surface interval before the next dive. The use of dive tables or dive computers is common in this scenario to track no-decompression limits, which indicate how long a diver can stay at a certain depth based on previous dives and surface time.

In general, the longer the surface interval following a dive, the longer your allowable time at depth for subsequent dives. After a dive to 60 feet for 50 minutes, and given a surface interval of one hour and 40 minutes, the subsequent maximum dive time decreases due to the residual nitrogen still in your system from the initial dive.

The answer of 19 minutes reflects a correct application of this table or computer, indicating that while you've had a considerable surface interval, the prior exposure at depth still affects your current limits. This means that you can safely dive again at 60 feet, but only for a limited duration to avoid excess nitrogen loading, which could lead to decompression sickness or other diving-related health issues.