Questions & explanations
1. You are paddling down a rapid and see a wave train that suddenly transforms into a hydraulic jump at the bottom. What physical factor causes this change, and how would you adjust your line?
The change from a wave train to a hydraulic jump often happens because the riverbed drops steeply, causing the water to accelerate and then decelerate abruptly. The wave train rides over shallow bumps, then the bottom slope increases, creating a deeper, faster flow that hits a downstream obstruction. To adjust, you should stop surfing the wave train early and prepare for the jump. Paddle hard to maintain speed so you don't get caught in the hole. Keep your boat pointed straight downstream. If you have good momentum, you may punch through the jump. Scout the rapid first to know where the change occurs.
2. Describe a scenario where a diver might need to perform an emergency ascent.
A scenario where an emergency ascent is needed: A diver is at 20 meters depth and suddenly their air supply fails completely. Their buddy is too far away to share air. The diver must immediately perform a controlled emergency swimming ascent (CESA). They drop their weights, inflate their BCD slightly for buoyancy, and start swimming upward while exhaling continuously. They ascend slowly to avoid decompression sickness. Once at the surface, they inflate their BCD fully, signal for help, and call for the boat. Emergency ascents are risky and should only be done when no other option exists.
3. Compare a boil line and a current seam. How are they alike and how are they different? Give an example of when each would help you pick a line.
Both boil lines and current seams are visual clues on the water surface that help you understand underwater features. A boil line is a row of boils indicating a submerged obstacle, like a rock ledge, while a current seam is the boundary between two different flows. They are alike because both guide line selection. They differ because a boil line warns of an obstacle you should avoid, whereas a current seam points to fast, clean water you want to use. For example, if you see a boil line across the river, you would paddle around it. If you see a seam, you would ride it to gain speed.
4. You see two boats: one with continuous rocker (smooth curve) and one with segmented rocker (a flat mid-section with curved ends). Which one is faster on a straight section, and why?
The segmented rocker boat is faster on a straight section because it has a flatter middle that rides lower in the water, creating more hull length to track straight. The continuous rocker boat has a constant curve, so less hull touches the water at any time, making it more nimble but slower in a straight line. For a long straightaway, the segmented rocker is more efficient. In tight rapids, the continuous rocker turns easier. Advanced paddlers choose based on the river: continuous for technical creeks, segmented for big water where you need both speed and maneuverability.
5. You see a wave train—a series of waves that do not move downstream. What causes this pattern, and how would you paddle through it to stay dry?
A wave train is caused by water flowing over a series of underwater bumps or rocks, creating repeating standing waves. The waves stay in place because the river's speed matches the obstacle spacing. To paddle through a wave train dry, you need to keep your boat speed the same as the current. Lean slightly upstream and use a forward stroke to punch through each wave. If you go too slow, the waves hit your chest; too fast and you may lose control. Aim to ride the troughs between waves, keeping your body relaxed. A wave train can be fun to surf if you catch the right one.
6. What is the difference between a wetsuit and a drysuit in how they keep you warm?
A wetsuit keeps you warm by trapping a layer of water against your skin and insulating with neoprene foam that contains tiny air bubbles. The foam reduces heat loss, and the trapped water warms up. A drysuit keeps you warm by creating a waterproof barrier that prevents water from touching your skin. You wear dry thermal undergarments underneath to provide insulation. The drysuit itself does not insulate; the undergarments do. Wetsuits are less effective in very cold water because the water layer cools quickly, whereas drysuits keep you dry and allow thicker insulation.
7. You are in a long downriver race and need to maintain a steady speed. Would you prefer a blade with dihedral (a ridge down the center) or a flat blade? Why?
In a long race, you want efficiency and stability per stroke. A blade with dihedral—a ridge that splits the blade into two faces—is generally better. The dihedral helps the blade stay stable in the water, reducing flutter and making each stroke smoother. It also allows a clean release at the end of the stroke. A flat blade can be less stable and may flutter, wasting energy. For steady speed, the dihedral blade gives more consistent power. However, flat blades are often used by experts who want a very aggressive catch. For long-term efficiency, choose dihedral.
8. What should you do if you feel ear pain while descending underwater?
Ear pain during descent is caused by pressure imbalance between the outside water and the air space in your middle ear. The correct action is to equalize the pressure. The most common method is the Valsalva maneuver: pinch your nose, close your mouth, and gently blow through your nose as if trying to clear your ears. This forces air into the eustachian tubes and equalizes the pressure. If you cannot equalize, you should stop descending, signal your buddy, and ascend a little until the pain stops. Never continue descending with ear pain, as it can cause injury.
9. How does a sinus squeeze differ from an ear squeeze?
A sinus squeeze is pain in the forehead, cheeks, or behind the eyes caused by pressure imbalance in the sinus cavities. It happens when the sinus openings are blocked by congestion or inflammation. An ear squeeze, medically called barotrauma of the ear, is pain in the ear due to pressure imbalance in the middle ear. Both are caused by failure to equalize, but they affect different areas. Treatment for both includes ascending to a shallower depth and treating the underlying congestion. Preventive measures include diving only when sinuses and ears are clear.
10. Give a drill to practice flip turns.
One simple drill is 'somersault in the water' away from the wall. Just practice flipping forward without pushing off. Then do 'flip and push off' from the wall with a gentle kick. Another drill is 'two kicks off the wall' where you do a flip turn and then take two dolphin kicks underwater before swimming. You can also practice 'flip turn with a noodle' to help you keep your body straight. A fifth drill is 'flip turn into a streamline hold' where you stay in streamline for three seconds after the push-off. Repeat these drills until the motion feels natural.
11. What are early signs of hypothermia that a diver should watch for?
Early signs of hypothermia include shivering, which is the body's attempt to generate heat. The diver may also feel clumsy or have trouble with fine motor skills, like working zippers or clips. They might become confused or have slurred speech. Other signs are feeling very cold, especially in the hands and feet, and a drop in the ability to think clearly. If you or your buddy shows these signs, end the dive immediately. Get out of the water, remove wet clothing, and warm up slowly with blankets or warm drinks. Severe hypothermia is a medical emergency.
12. Compare a pre-workout snack and a post-workout meal.
A pre-workout snack is eaten about 1-2 hours before swimming. It should be mostly carbohydrates for quick energy, like a banana or whole grain toast. It should be light so you don't feel full in the water. A post-workout meal is eaten after practice and includes both carbs and protein. For example, a peanut butter sandwich is good after, but not right before because it has fat that slows digestion. Pre-workout snacks give immediate fuel, while post-workout meals help recovery. Both are important, but they have different goals. Timing matters for both.