19 April, 2000

Diver Communication

Question 60: How do whales use baleen in feeding?

When we dive underwater, we have a regulator in our mouth, water in our ears, a limited field of vision, and we move slowly. Effective communication can be both difficult and vital. For common queries there are hand signals that are more or less universal. Before we dive with someone new, however, we always verify what each signal means at the surface.

An "ok" sign means just that. It is used both as a question, "Are you ok?", and as an answer between buddies, most often while descending and occasionally during the dive. Buddies descend close together, as it is at the beginning of a dive with its rapidly-increasing depth that most problems appear. One buddy may have difficulty equalizing his ears, notice a hole in a glove, see a seal nearby, or identify a problem with his regulators. Once at the bottom, each diver checks his gear and uses the "ok" sign to let his buddy know that everything is good and they are set for the dive.

Another common signal we use is a decisive directional movement with lower arm and hand held with thumb up and fingers together to show which way we will swim. We also use signals for changing depth. At the surface we follow the "ok" signal with a thumbs down sign that shows we are ready to descend. A thumbs up signal underwater is the sign that it is time to begin our ascent to the surface. Waving our hand back and forth with the palm down indicates that we want our buddy to level off and hold at that depth. A signal unique to Antarctic diving is one for a leopard seal, a chomping motion made with thumb and fingers coming together as if we are making a hand puppet talk. During most of the dive, buddies are not at each other's elbows so it is important to be able to attract attention. Metal-tapping noises carry well underwater. Since we all have dive knives to assist with collecting, tapping them against the air tank usually works well. One downside is that it is almost impossible to determine the direction a sound is coming from underwater, so a signaled diver will usually end up doing a quick 360 turn to identify the source.

We also need to be able to communicate with the boat. When divers enter the water and when they resurface, the first priority is to let the tenders on the boat know either that the divers are ok or that they need help. The signal for "ok" at the surface is making a fist with one hand and tapping it on top of your head. Like the diver-to-diver version, it can be a question (from the boat) or an answer (from the divers).

Since we are in an area where there can be other boat traffic, boat to boat communication is important also. Other boats need to know what area to avoid. Boat propellers pose a danger to surfacing divers. A dive flag, red with a white diagonal stripe, usually lets others know that there are divers underwater at that location, but we have no good place to fly one on our Zodiac. We rely instead on the station communication system to let everyone know where divers are. When we reach the dive site, when we put divers in the water, and when we take them out, we call in to the station on the area VHF frequency and announce the fact.

Today the weather is whipping wind with a little precipitation thrown in. Walking outside is unpleasant, and the waves are too high to go out diving. Everyone in our science group is working in the lab or reviewing and writing scientific papers. During tonight's Wednesday night science lecture we will show some of the underwater video footage that we have taken in the area. The whole station comes to find out a little more about the science they work so hard to support.

Answer 59: In the Southern Ocean, these filter feeders include the blue, fin, minke, humpback, sei and southern right whales.