What surface interval is required in order to do a dive to 70' for 35 minutes followed by a dive to 50' for 35 minutes?

For a dive to 70 feet for 35 minutes followed by a dive to 50 feet for 35 minutes, the required surface interval is influenced by the principle of nitrogen absorption during dives and the need for adequate off-gassing to mitigate the risk of decompression sickness, or "the bends."

In this scenario, both dives are relatively deep and of considerable duration, resulting in a significant accumulation of nitrogen in the body. Diving tables or computer algorithms are typically used to determine the necessary surface interval between dives to allow the body to off-gas the absorbed nitrogen effectively.

After completing a dive to 70 feet, a specific surface interval is mandated before safely embarking on a second dive at a shallower depth. Generally, the deeper and longer the first dive, the longer the necessitated surface interval to ensure a safe ascent to the next dive.

A surface interval of 60 minutes is a prudent choice in this case. In practice, this longer interval allows for sufficient off-gassing, aligning with recreational diving standards and safety practices. Each diver should always refer to dive tables or computers to ascertain the appropriate surface interval based on their dive profile, but for this scenario, a 60-minute surface interval is well-established as necessary for safe diving following