The U.S. Coast Guard cutter George M. Bibb (Builder's No. CG-71) was built at the Charleston Navy Yard, Charleston, South Carolina, and was launched in 1937. She was commissioned on 10 March 1937. The ship was 327 feet in length, with a draft of 12 and a half feet. Her propelling plant consisted of twin propellers powered by geared turbines supplied with steam from oil fired boilers. The first assignment of George M. Bibb after her commissioning was to the Fifth Coast Guard District, with Norfolk as her home port. Sometime in May or June of 1937 her named was shortened to Bibb.
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The issue with diving—at least for this discussion—is that as a diver descends in the water column, he or she has no option but to breathe compressed gas. Because of this, the inert gas contained in whatever is being breathed is stored in the diver’s body. This is sometimes called inert gas uptake.
At the end of a dive, on the way back to the surface, the process is reversed, the stored inert gas is released by the diver’s body. This is called inert gas elimination, or more simply, decompression. These two processes are part of every dive—even seemingly benign sport dives to shallow depths for short periods of time. Every dive really is a decompression dive.
When diving, tracking and understanding how to best manage inert gas uptake and decompression within safe limits, is second only to making sure one has something other than water to breathe. If we “get it wrong” and remain at depth too long, ascend too rapidly, breathe the wrong gas, or simply have a bad-luck day, we run a higher than usual risk of suffering decompression sickness (DCS). Getting bent, the colloquial term for DCS, is a collection of disorders caused by a portion of the inert gas stored in a diver’s body bubbling out of solution too rapidly. The consequences of being bent run the gamut from nausea, fatigue, mild joint pain and dizziness all the way through paralysis and death.
Often referred to as slugs due to their evolutionary path, the grand designs of nudibranchs are as fascinating and varied as there are slugs themselves. Each one of them has evolved in a special manner to survive and reproduce in the many different and challenging habitats in which they are found. Cold water to warm water, benthic or pelagic and at every depth, nudibranchs occur globally and have even been found in brackish rivers.
Shooting photos of sea slugs is often the way many macro shooters start out. They shoot various finds from each dive, then look them up in a marine species identification book. This often results in a collection of basic ID photos. While this is a common path for an underwater photographer to take in learning the craft, it often sets one up for bad habits down the road. There eventually comes a time when shooters have the desire to take their images to a different level, but breaking the habit of shooting ID photos can often be a challenge. One of the things that has helped me to shoot more creative images of nudibranchs began with learning about them first.
Knowing the food source of a nudibranch is an elementary yet effective way for hunting nudibranchs. Tunicates and algae are a great place to start, followed by hydroids and so on. It also helps to know a little about the anatomy and biology of nudibranchs.
Mollusks comprise a group of soft-bodied animals that includes snails, clams, and sea slugs. The most common characteristic of most mollusks is their shell. One of the largest groups, the snails, is renowned for their shells. Snails are univalves, which means they have one shell. And it is this shell that for many people is the epitome of the ocean. There is perhaps no other ocean treasure that displays more diversity and beauty than the shell. Conchology, the study and collection of shells is a popular hobby the world over. The bivalves, or two-shell mollusks include the clams, scallops, and oysters. It is the oyster that is responsible for producing the most coveted of the ocean's treasures - the pearl. Still other mollusks have lost their shells altogether. The octopus, the squid, and the sea slugs have evolved their own survival strategies to replace their protective armor. Indeed, it is due to the absence of a protective shell the octopus has evolved the largest and most complex brain of all the mollusks. Below is a listing of some of the most common mollusks found on the world's coral reefs.
Beaked whales are members of the family Ziphiidae, the second largest family of cetaceans (which includes whales, dolphins and porpoises), however many of the 22 species of beaked whales are among the least known or understood mammals in the world. This lack of knowledge is highlighted by the fact that three new species of beaked whales have been discovered in just the last two decades.
To see beaked whales at sea is such a rare event that many researchers devoting their life to study cetaceans have never seen one. Living in deep waters, usually far offshore, these creatures spend some 92% of their time underwater, invisible to humans. Beaked whales break diving records, feeding at depths that can reach three kilometers and last up to 2 hours. After these diving feats, they rest, performing shorter and shallower dives with brief surfacing intervals. These behaviors, together with the fact that beaked whales live in small groups, are not usually attracted to boats, and do not perform aerial acrobatics as much as dolphins, mean that beaked whales are not easy to detect at sea. Moreover, many beaked whales have variable color patterns that may be shared by other ziphiid species, challenging the identification of beaked whales at the species level during sea encounters, when often only a short glimpse of their body is achieved.