I want to share an experience we had while diving White Fish Point by the lighthouse in Lake Superior. We dove off of the beach, "everyone" knows sand ripples form parallel to shore so we were navigating across the sand flats perpendicular to the sand ripples. We were cruising in 7-10 feet of water with good visibility but nothing to see except sand and the occasional stick. We dropped to 17 feet and I noticed we were suddenly swimming parallel to the sand ripples. I had to stop. I KNEW we hadn't turned 90 degrees, the compass was pointing the right direction and I knew I hadn't felt my body make that kind of turn. The relationship to the sand ripples was screwing with my head and my buddy and I had a confused conversation. We opted to ignore the natural navigation cue and continued along our compass heading. We were soon back in 7-10 foot water and the ripples changed back to their original orientation, parallel to shore. I found that to be quite a relief and proof that I wasn't crazy
We found another deep area and once again the ripples changed direction, back in the shallow they were parallel to shore. Our dive went out about 300 yards or so and crossed a total of 3 "ditches" with sand ripples going the "wrong way." Returning we counted the ditches and saw the one large stick we had seen on the way out.
I'm guessing the reason the ripples were perpendicular in the deep areas was due to a current running parallel to shore. The current dug out the trenches and changed the sand ripple direction. It taught me that sometimes mother nature breaks "the rules" and you have to be able to decide if your navigation is in error or if you're being thrown a curve.
Another story:
A couple years ago I had a student who was doing the navigation part of his advanced class in a local quarry. I was diving with him since he was the odd man out. I assigned a point for him to start underwater and he was to carry a jug on a heading and drop it off then return to the point, pick up another jug and place it on another heading. We would do that for 3 jugs then he would brief the second team so they could go out and retrieve the jugs. There is a line that goes to the bow of the wooden boat we were using as a starting point. He navigated out, placed the first jug and navigated back toward the boat. We were just out of sight of the boat when he made a 90 degree left turn, crossed the line and was swimming into never never land. I rounded him up and brought him back to the boat and we surfaced to find out what happened, he said he was following his compass. I told him he was allowed to follow the line if he thought the compass had done something weird. We went back down and he picked up the second jug, navigated out and placed it but on the return to the starting point made and even more abrupt turn, crossing the line and heading into the distance. I rounded him up and we went to the surface this time. I admit I was aggravated because if nothing else when he got to that line he should have followed it to the boat not crossed it since its relationship to the boat was obvious when we left our starting point. "Can you find your butt with both hands?" probably shouldn't have been the first thing out of my mouth but I had told him not to cross that line. We went back down and placed the third buoy and he was able to get us back to shore easily enough.
He briefed the other buddy pair and they went out to retrieve what we had set. I was watching their bubbles as they went toward the first buoy, turned around and headed back to the boat. Suddenly their bubbles made the same 90 degree turn we had made. I saw that buddy pair find the line and follow it back to the boat. They started out on their next heading, found the buoy and on the return their bubbles made an abrupt turn in the same place we had but again I saw them follow the line to the boat. I apologized to my student for chewing on him, there is evidently metal in the bottom of the quarry below the mud that screws with your compass as you get to that point. We all learned a compass lesson that day. Sometimes you have to question what the compass is telling you. If your body didn't make an abrupt turn and you have the compass level it shouldn't be showing abrupt direction changes. A metal wreck will screw with your compass but so will unseen metal under the muck.
You have to do some thinking when navigating but it's good to stimulate your brain underwater.
Expect to have days when you can't find your butt with both hands. I was taking an advanced class on a night dive at the local quarry. I have oodles of dives in that quarry and can navigate it without a compass just by looking at the scenery. I was buddied with one of my former students and had a couple of DM's with me. We were starting from a dock I don't normally use and the visibility was horrid. There was so much silt in the water that I had vertigo. I found my turn spot and headed away from the wall toward the attractions in the middle of the quarry. I needed to get to the motorcycle and then hit the rest of the sites. I never saw the motorcycle but thought I had gone too far so I made my turn. The DM said he was wondering why I turned since he could see the motorcycle just a little beyond us. I was totally lost thanks to the vertigo and even using my compass wasn't helping. I finally had to tell my DM to lead us back.
I took some ribbing from the students for getting lost, they said they wondered what I was doing since they had seen the motorcycle as well but I hadn't gone to it. The former student I was buddied with said, "I knew we were in trouble when you took out your compass and still couldn't find your way." The DM's wanted to know why I hadn't gone on to the motorcycle. I was so disoriented from the sediment induced vertigo I never even saw it even though we passed within about 20 feet of it. Just because I'm an instructor doesn't mean I'm going to get it right every time. I try to impress upon my students that just because they are new doesn't mean they can't lead a dive. I encourage them to speak up when something doesn't seem right, I'm not above taking a correction from a student underwater
I've also introduced more navigation into my open water check out dives. I lead the first dive to show them around then they start leading dives. Our quarry is simple to navigate and it's fun to see them discover they can start and end a dive at the same spot.
Ber :lilbunny:
