What is a key action to prevent fast ascent during a dive?

The key action to prevent fast ascent during a dive is to close depth monitoring with surface/topside control. This practice is vital as it creates a systematic check on the diver's ascent rate. When divers have reliable communication and control with the surface team, they can receive timely guidance and assistance, which can help in maintaining an appropriate ascent rate.

Monitoring depth properly allows divers to keep track of how quickly they are ascending and adjust their ascent accordingly. The communication can also ensure that divers are adhering to standards regarding safe ascent rates to reduce the risk of decompression sickness, which can occur if a diver ascends too quickly. Therefore, having a control mechanism in place contributes significantly to safe diving practices.

Using a buoyancy control device also aids in managing ascent rates, but it is the connection and monitoring with topside control that provides the additional oversight crucial for ensuring safety in deeper dives.