I've done a bit of research on this. The text appearing below, in light
of bandwidth, is often shortened. The URL's give the full text.

Case 1:

> Believed to be the first reported case of envenomation by  Astrotia stokesii in Australia.  In October 1979, a two year old girl began screaming while playing in the water at a beach 3km from Yeppoon, Queensland.
The photograph illustrates the snake involved and the appearance of the
child's foot, showing multiple bite marks suggestive of severe envenomation.

Case 2:

> Using a custom-built aquarium at the Smithsonian Tropical Research Institute, photographer Carl Hansen got this close-up view of deadly Yellow Bellied Sea Snakes (Pelamis platurus). Captured for study by STRI scientists, they have the most toxic venom of any snake. There is no known antivenom for their bite.
"Fortunately," says Hansen, "these snakes are not aggressive and rarely
try to bite even if handled. They are highly modified for life in the
open Pacific Ocean and are unable to crawl on land. They can often be
seen floating along drift lines on the surface, but spend much of their
time in deep dives."

Case 3:

I couldn't copy the text on this site, some interesting observations though.

What follows comes from my friend (Dr of Marine Biology) David
Wachenfeld of the Great Barrier Reef Marine Park Authority:

There are about seventy species of snake that inhabit the sea and/or
estuaries. To
the best of my knowledge, about seven of these are known to have caused human
fatalities. Just one of these species is single handedly responsible for
about 90% of recorded human fatalities from sea snake bite. However,
this species inhabits
muddy estuaries and so does not commonly come into contact with people
in Australia. Interestingly, Australia's foremost sea snake researcher
contends that there have been no substantiated human fatalities from sea
snake bite in Australian waters. It is worth noting that, in the species
that have been studied, in around 70% of bites made in self defense, the
sea snake with-holds the venom and the bite is merely a physical trauma,
not a toxic one.

The factors that determine how dangerous a snake is are mostly- fang
length, aggressiveness, dose of venom delivered and toxicity of venom.
All four factors vary alot between different species of sea snake. There
are three species of sea
snake that feed on fish eggs. These have small fangs and venom of low
toxicity and can probably be considered as unable to kill a person.
Pretty much all other
species should be considered potentially lethal to humans. For divers,
it's worth noting that most sea snakes have fangs less than 4mm in
length and therefore are unlikely to be able to penetrate a wet suit of
reasonable thickness. Olive sea snakes (fangs up to 4.7mm) and Stokes
sea snakes (fangs up to 6.7mm) can both penetrate wet suits but I'm not
aware of human fatalities from either species. Also, the species that
inhabit coral reefs, where most people do most diving are generally not
aggressive to people (assuming the people don't deliberately harass the snakes!).

Snakes are able to dislocate their lower jaw. But, exactly as you say,
they do this
to enable them to swallow large prey. Some sea snakes can swallow prey
twice their own girth. But the dislocation ability of the lower jaw is
only used to increase
swallowing capacity not biting capacity. Snakes also have kinetic
skulls. This means that the bones of the skull are not fused but can
move relative to each other. This means that, when a snake has prey in
its mouth, it can hold onto the prey with the teeth on one side, flex
the skull and move the teeth on the other side forward on the prey. In
this way, the snake can 'walk' the prey further into its mouth without
ever actually letting go. Generally speaking of the 'ear-lobe or finger'.

As to that last I suggested to him that I had thought that small
extremities, such as the ear lobe and finger, were more vulnerable to a
bite than anything larger and that I did not believe that snakes
generally dislocated their jaws prior to an attack.

As an amusing aside, he also said (partly in defence of a somewhat late reply):

> I was lecturing in reef ecology on a ship called the World Discoverer. You may have seen it on the news as it hit a reef in the Solomons and nearly sank about five
days after I disembarked. Bloody good timing on my part.