Archive for January, 2011

How Long can a Scuba Diver Stay Underwater?

Sunday, January 30th, 2011

I provided a simple answer to this question in a post last winter.  Over the past year, this post received a large number of hits, so it’s obviously this is a question that is often asked.   Therefore, I wanted to expound on the previous post.

There is no short answer to this question.  Ultimately, the limiting factor is either available gas, or environment.   The environmental factor here is cold.  Water transfers heat 25 times faster than air.  Even 80 degree water robs your body of heat.  This is why exposure protection is needed.  For the rest of this discussion, let’s assume there is sufficient exposure protection for the given water temperature.

Now the time limit is just a function of the available gas.  Let’s breakdown the answer based on type of diver.

Free Diving: Here the divers plunge to some amazing depths on one breath of air, and stay for several minutes before returning to the surface.  The limiting factor is the individuals tolerance for low Oxygen, and high CO2. I believe the current record is 124 M unassisted.  The maximum duration for static (resting) breath hold is 11 minutes 35 seconds.

Basic Scuba Diving: Here there are two limits:  The available gas in the diver’s tanks, and the no decompression limit for the depth.   There is a detailed explanation of the factors involved, but an average diver can stay between 60-80 ft for about an hour.

Technical Diving: Divers are limited by the number of tanks they use during the dive.  Some exceptional dives have been for over 18 hours.  Clearly a great deal of planning is required for these types of dives.  More routinely Technical Divers often go to 150-250 ft with durations around 90-120 minutes.

Rebreather Diving: A rebreather (as described here) removes the gas limitation, but imposes a limit on the duration of the scrubber material.  Based on the construction of the rebreather, this is usually between 3 and 11 hours.  The limiting factor here is the number of tanks a diver is willing to bring in case of rebreather failure.

Commercial Diving: These divers are provided gas from a surface vessel or station.  This technique also referred to as surface supplied, does not have a limit on the gas available.

Saturation Diving: In this case the divers body is completely saturated with inert gas.  In some cases the divers will utilize a habitat between dives.  This provides an area where the diver can warm up, and take food and liquids.  In essence there is no limit to the duration that a diver can live in saturation.  The down side is the extremely long time needed to decompress.

I hope this helps answer the question.   If you have any questions on this subject, send me a comment below.

The Butterfly Forest

Saturday, January 15th, 2011
Butterfly Forest

Butterfly Forest

Okay, it’s not diving related, but while Val and I were in Florida, we had some time to kill.  Dali recommended the butterfly forest exhibit at the Florida University, Museum of Natural History. Given that Val has planted a butterfly friendly garden in our backyard, she was definitely interested.  As a nature lover, I was happy to join her.  After consulting the GPS, we jumped in the car and headed down.

When we entered the Museum, we discovered that there were several other exhibits.  The butterfly forest was only one of them.  On entry to the butterfly exhibit, the walls are covered floor to ceiling with display cases.  It quickly reminds you of the diversity of this order.

The forest itself was screened in, so the cool weather limited the activity.  Butterflies are most active when the weather is warm.  As the sun warmed the rocks and structure of the building, they became more active.   We walked around the exhibit taking pictures and reading the signs.  Several time a day one of the researchers at the museum come out and releases some of the newly hatched butterflies into the exhibit.  During this period they talked about the different species and the research going on there.

On the way out we stopped by the incubation area, where there were rows of chrysalis were hanging prior to hatching.  Here and there a newly hatched adult could be seen spreading their wings for the first time.

We spent a few hours touring the rest of the museum, learning about stages of Florida’s wildlife development over the past few million years.

If you get a chance, stop by, it’s great fun. Thanks, Dali for the recommendation.

Manatee Excursion 2011

Thursday, January 13th, 2011
Is that my reflection?

Is that my reflection?

Val and I had the opportunity to join Becky and Dave on their annual winter manatee trip down to Crystal River, Florida.  We packed our gear and headed down to Tampa.  An hour later, we were pulling up to the hotel in Crystal River.  Over the last few years, I’ve had some great trips down to this area.  There’s been a load of training for myself, as well as my training others.   The caves and sinkholes are difficult to blow out, so it’s a good area for scuba training for deep dives.

This trip was just for fun.  We planned to dive with the manatees, then spend the weekend relaxing.    Unfortunately, the weather was not cooperative.  We left NJ just after a snowstorm.  This winter has been one of the coldest I remember.  Now that we were down in Florida, we were hoping for a little warmth.   No such luck.  Thursday morning was in the 30s with a bit of a breeze.

With the cooler conditions, Becky decided to keep the boat trip short, and head to King’s Springs.  The water clarity is not as good here, but the Manatees were active, and inquisitive.   While you were petting one manatee, another would come up behind you and nudge you for attention.  Staying in the water was the key to keeping warm.  During the entire day, there was steam rising off the surface.  Yes, it was quite cold when we got out.  After getting lots of photos, we headed back to the shore to warm up.  While it may have been cold, we had a lot of fun.

Sanctuary

Sanctuary

Val had filled her fun quota that day, and decided to head to Homosassa Spring Wildlife State Park on Friday.  Apparently this is a wildlife preserve that also provides wildlife rescue services.  There she found many animals that had been rescued, and were now recovering before release.

The weather caused a few cancellations on Becky’s next trip, so there was room for me to join them again.  Friday, the manatee excursion headed out to the Three Sisters Spring.  There is a large sanctuary area around the springs that was filled with manatees.   Most were quietly resting, but some would come out of the sanctuary and interact with the divers.  Speaking of divers, there were quite a few.  Probably because it was warmer, but also because it was Friday.  When we arrived there were 5 boats, and numerous kayaks.    With this many people I’m sure it can be overwhelming to the Manatees.  Everyone stayed away from the sanctuaries to give the manatees their space.  Most of our crew were experienced divers, and very calm and careful in the water.  This made the manatees more relaxed, and many freely interacted with us.

Becky and Camera

Becky and Camera

Back in the springs, the water was crystal clear and warm (72), but there were very few manatees, and they were resting.  (You can’t disturb them when they are resting.)  We got a few shots of the one or two in the springs, then headed back to the river where they were more active.

After several hours trying different photo techniques, angles, and subject, we headed back to the boat.  The ride back was much warmer this day.  We quickly got changed and headed out for some hot food to warm up.