What does a diver need to do before ascending to the surface?

Before ascending to the surface, it is essential for a diver to signal their buddy and check their air supply. This step ensures that both the diver and their buddy are aware of each other's status and readiness for ascent. Communication is key in diving safety, as it allows divers to confirm they have sufficient air for the ascent and to make sure both parties are prepared to safely execute the ascent together.

Maintaining proper buddy communication is critical in ensuring that divers can assist each other as needed, particularly during an ascent where potential issues like rapid ascents or equipment malfunctions can occur. Checking the air supply confirms that the diver has enough air to safely ascend and conduct necessary safety stops, which are crucial in preventing decompression sickness.

Other options may seem relevant but do not encompass the overall safety protocol for ascending. While increasing buoyancy, equalizing ears, and changing tanks are all important aspects of diving, they are secondary to verifying communication and air supply before starting the ascent. Hence, signaling and checking air ensures the diver's safety and preparedness for the ascent.