For most people, getting into a cage and being lowered into the ocean with great white sharks encircling is extreme enough.
But this clearly isn't the case for these two daredevils.
The amazing underwater pictures were taken by Scottish snapper David Litchfield, who has taken the same risk to get shots of one of the world's most fearsome predators.
Mr Litchfield, a computer security expert, was diving off the Isla de Guadalupe, a hotspot for great white sharks in Mexico.
The 36-year-old said: 'Cage diving with great white sharks is thrilling.
'Standing on top of the cage as these huge fish swim around eyeballing you, makes it doubly so.
'There is intelligence behind those eyes - a sense of curiosity - but as long as you maintain eye contact with the shark it's not likely to take an exploratory nibble.
'Indeed, photographers can get their cameras really close with no aggressive response from the shark.
'The "smiling" shark photograph was taken whilst the shark's nose was touching my camera's dome port.'
Mr Litchfield said that the cages were lowered to 40 feet below the surface, adding: 'It gets you that little bit closer and give you more of a thrill.
'It really is an experience. Sometimes you get a hell of a fright when they suddenly appear.
'They are ambush predators and they do sneak up. One moment you're gazing into the depths with nothing around and suddenly it's there, right on your shoulder.'
Mr Litchfield, who lives in Cellardyke, close to St Andrews, competed as a track and field athlete for Scotland.
He was the Scottish Under 20 Champion for both the long jump and decathlon and is the holder of the Scottish Schools Indoor record for long jump.
He added: 'In the picture we can see two divers standing on the cage as the shark turns up to investigate.
'The chains holding up the cage provide welcome cover but if things get too close for comfort it's possible just to drop into the cage.
'The shark in the picture is a five-metre female and the marks down her side were not caused by a boat's propeller but are more than likely love bites - literally: males, being shorter than females, have to bite on when they copulate.'