I was not planning to react anymore, but after reading Joel's reaction I laughed because he did mention some very pratical points. The most important point maybe is his remark about the insurance on which you did not comment, PhDiver. If you dive alone....no point..it's you yourself who will has to bear the consequences of a non-covered insurance i.c.o. a dive accident. Be aware: whatever the real cause of that dive accident might be, the insurance co. will very likely not pay you the cost for treatments. But if you have taken newcomers with you (as you do), I'm pretty sure you will be held responsible in case a dive accident also affects that newcomer. I believe you are cautious with what you're doing but as you will know for sure, even at 50 feet a long dive can cause a serious dive accident when unexpected things do happen. Reading Joel's comments I also realize how personal some arguments can be. For instance: I'm always filming here U.W., have a dive suit of 0 mm (yes, I never use any other 'suit' than a T-shirt in tropical waters) and stay very often 90 minutes under water. I often get allowance from the dive organisation to stay longer than the standard max. time of 60 minutes. These dives start mostly at depthes of around 100 feet and finish at 10 feet (non-deco dives). Special dives go much deeper and are of course deco-dives. I know that divers look very surprised when they see me after the dive coming into the boat without shivering, they sitting their with a 5mm suit. Sure, also my body cools down, but I have in general more problems with higher than lower temps. Shivering (when serious) is a sign to end my dive. Also the consumption of camera batteries (in my case a video camera) is quite case dependend (personal). At the end of a dive I have mostly not used more than 30 % of the battery capacity. I'm filming quite selective. 15 minutes of recording is about the max. during 1 dive (of maybe 90 minutes). Sometimes only 5 minutes recorded ! All I want to say: many items will differ from person to person, but some will not. These have to be taken very serious. You can never predict someones behaviour under certain circumstances. What e.g. if a newcomer suddenly makes an emergency ascend from 50 feet. Are we 100% sure that we in all cases can prevent him from doing so and are we sure he will apply what we told him before his first dive: to exhale !!!! I won't say YES to this question. Problems have even arised in a swimming pool with students !! I'm a CMAS instuctor for 25 years. Luckily I suffered no serious dive accidents with my students, neither with me or my buddies although some of my dives COULD have ended badly (if some factors had been different). My advise: take care and especially don't promote this Dive-Sled activity with non-divers to prevent liability or stay within a really harmless depth. There are enough examples to be given of people brought to court and declared guilty because they were found responsible for an accident. These examples we got during our instructor training and we still get them if new ones occur.