I had two incidents last week (it's Sunday morning of labour Day Weekend as I'm writing this): On Tuesday, I went on a charter dive on the St. Lawrence River in Brockville,Ontario. There was a strong current, but nothing insurmountable. The boat was tied off at a buoy, and there was a 2" diameter rope running from the aft of he boat to the bow, and eventually to the buoy. I was the first to enter the water: I jumped in, wing partly inflated floated up to the surface - everything OK so I motion to the Captain my OK, and I swim the the bow of the boat to grab a hold of the rope. As I'm waiting for the rest of our group, I find myself struggling to breath properly. I get the feeling of Co2 retention, so I close my eyes and try to lax and take deep breaths, and exhale completely. It doesn't work, and I start to get a headache, and I decided then to cancel my dive. I swam to the back of the boat (still feeling panicky, but less as I get back in the boat). After I got on, I had wobbly legs, feeling of dizziness, weakness, and a headache. I attributed this to low blood sugar levels as I had not eaten anything for almost 5 hours prior. I had drank fluids before the dive, so I don't think it was dehydration. After the I got back on chore, I took some pain killers and ate dinner, and the next morning I felt good, although a bit tired. On Friday, I decided to do a shore dive on a lake (i.e. no current). I knew the waters pretty well, and I made sure I was well-fed, well-hydrated, and that my gear was working well(checked regulator pressure (low pressure was 140 psig as per the manufacturer's instructions). I inflate my wing, and use my snorkel as I'm swimming on the surface to deeper waters. I'm making sure I am not exerting myself physically, and that my breathing is normal. When I get to waters that are about 5-6 feet deep I decide to go underwater. So I switch to my regulator, and breath for a while on the surface with it to get accustomed to it. After I feel I am breathing OK, I deflate my wing, and descend to the bottom. I swim down slowly to 10-11 feet, and was using my fins a bit, but not much - I was just swimming slowly, observing fish, etc... All of a sudden I get that feeling of Co2 retention, and get that shortness of breath. So instead of bolting up to the surface, I do as I was instructed to do, and stop, relax, close y eyes, concentrate on taking deep breaths, and on exhaling them completely so I don't get Co2 retention. Well, that didn't last very long. After about 10 minutes underwater, I surfaced. Since I had only been 10 feet down, and only for a short time, I didn't think I needed to do anything other than surface and inflate my wing, and swim to shore. Now I don't know how long I took to surface, but suppose I didn't do it in 10 seconds (following the 1 second per foot rule), but most likely in 5 seconds... I then surfaced, and had a panic attack. I knew I wanted t rip off all my gear and swim ashore (I was about 100 feet from being able to touch the bottom with my feet), but I kept my head on my shoulders, and started to swim to shore with my gear on. I was very low on energy at that point, so I called out to a guy on shore and asked for help. he swam out to me, and helped me back to shore. By the time I got on sore, I had a pounding headache and my neck muscles on he back of my neck hurt real bad. I felt almost nauseous , very week (BTW, I had not over-exerted myself - I run, hike, etc... a lot more than what energy I expended then - I was doing very relaxed dive), but the main thing was this splitting head ache that hurt with every beat of my heart. That headache and neck pain started at 4:30 ish when I had the panic attack, and got a bit better once I got back to camp. All day Saturday I still had the headache and neck pain (ibuprofen is helping a bit, but not much). If I was to chart t pain levels with 10/10 being 4:30 Friday, by Saturday morning it was about 7.5/10, and this morning 9:00 AM Sunday it's about a 5.5/10 Any ideas why I have this headache and neck pain? As it's the long weekend, i won't be able to see a specialist for a couple days, and I don't trust the emergency room doctors (that got stuck with the Labour Day Weekend ****) at the local hospital (I'm back at home in the middle of farmland) to know anything about diving accidents. My main confusion centres around the fact that I was only at 10 feet and only 10 minutes underwater and not under physical exertion. Also, I knew my regulator was OK since I had used it on multiple dives a couple weeks prior, and checked the delivery pressure - I also made sure the valve was open all the was by taking deep breaths ad checking for the pressure gauge to make sure it didn't go down (indicating a problem with the regulator or a partially-open valve). Thanks.