Hammer is hot
Some twenty years ago an encounter with the great hammerhead (GH) was a rare experience for underwater photographers. The best place and chance to meet them was at Tiger Beach, Bahamas where they occasionally mixed in with the regular lemon, carribean reef and tiger sharks. When a GH showed up, a crew member of the boat started yelling "hammer, hammer' which was a signal to rush in the water to meet the fabulous creature. Some were lucky others not. Some years later the scene changed radically. At Bimini not so far from Tiger Beach GHs became regular customers, which increased the chance that the visitor could take home some awesome shots of this apex predator. The GH became 'hot'. Even the mighty tiger shark had to make way for the GH with its spectacular dorsal fin, swinging radar-shaped head and black bulging eyes. Moving slowly in the clear blue water above the flat sandy bottom, apparently willing to approach and 'pose' for the UW photographer.
Using the fish eye I personally like using the fish-eye lense, although it may cause some perspective distortion. In particular the big hammmer may reach enormous proportions relative to more distant parts of the body, when the shark gets very close (around 50 cm) to the mini dome. With a shark coming that close your technique resembles that of CFWA (Close Focus Wide Angle), which is normally used to focus on small colourful objects with an interesting background. Meaning that you need to pull your strobes close and somewhat backward to the housing. The advantage is that details of the head come out razor sharp. Keeping a larger distance (say 1-2 meters) will diminish the distortion, at the cost of some loss of the crispness of details. With a primary lense you may need need a converter or crop the image in Photoshop. If you possess a Tokina 10-17 lense zooming in a bit will have about the same effect. With the shark further away, your strobes need to extend more forward and distant from the housing.
GHs near Forida GHs now even show up regularly at the other side of the gulf stream, at Jupiter, West Palm Beach. Here a variety of sharks can be encountered at more remote locations in open water, where baiting is permitted. The dives are not so easy since they often take place in deeper water with a strong current. But the shots I have seen sofar are truly spectacular. On can only hope that the charters with shark friendly visitors that operate in these areas will contribute to more respect for the apex predators. That are still hunted down in US coastal waters where they lack the protection they have in the Bahamas, by professional as wel as sport fishermen. Especially lemon sharks now aggregate in large numbers in the Jupiter area. Since the season for commercial and recreational shark fishing season has been opened in Januari this year, shark protectors fear that this will cause many shark victims. See also: http://fusion.net/story/286584/under-siege-how-fishing-is-threatening-floridas-sharks/