Crocodile Vs. Shark

Salt water crocodiles are known to feed on Bull sharks of considerable size frequently.It doesnt matter to a saltwater crocodile whether the water is  10 or 15 feet deep.It is known to be a good swimmer and many cases of crocodiles crossing oceans (ie more than 1000miles) had been recorded and also some species of sharks are known to be on the menu of Salties.

The photograph above is from Telegraph. 

The sizes of the Great white sharks are often exagerrated to beyond 25 fts and more majority of the adult great whites ranges from 16ft to 20 fts.One great white caught in Taiwan in 1997 was 23ft long and weighed  2500kg

The average length of  a saltwater crocodile is also the same ie 16 to 20 fts. A saltwater crocodile exceeding 23fts(7meters) at Bhitarkanika wild life Sanctuary of Orissa state in India Bhitarkanika is attested by Guinnes.

Crocodiles are very territotial and are good fighters also.Male crocodiles often have territorial wars resulting in ripping of limbs and other body parts.

My understanding about Great white is that its a hunter which thoroughly recognises its prey.And its(big sharks) diet consists of marine mammals with high fat content especially seals and other sharks and large fishes,also it is known to scavange on whales.So a croc doesnt come in its menu.So attacking a croc from below for no purpose seems impossible, and sharks are not known to be territorial.And even though sharks and fishes comes in its menu , I dont think a croc will take the risk of  attacking a shark of its own size unless it is for territory,Crocs are protective of its territory but while crossing the sea it will be well aware that its not in its territory.

A situation in which both knows each others presence the results one cannot predict.Soch a fight will result in severe injuries on both sides

Crocs are known to survive large wounds and even loss of limbs during territorial wars.But a shark with large injuries are not known to have survived

A crocodiles body compared to marine mammals is more muscular and is covered with thicker skin with scales.It can withstand deadly crushing  bites from other crocs during territorial fights and it survives even after losing limps and body parts.So if a shark bites a croc it may injure it but not kill it ie a croc which survives a 5000Psi bite of its own kind can easily survive a 800psi bite of a shark, but if a croc bites a shark things will be different.The cartilageous bones of the shark of whichever area croc is biting will get crushed and if the croc holds on to it,I dont think the shark will pull the croc which is 3/4th its(shark's) body weight along with it while swimming.

A 19/20 feet croc will have a jaw line which is more than 3 feets long, which will enable it to bite  and hold on to a substantially big part of the sharks body.If it bites a fleshy part it will rip off and will leave the shark severely injured.If it is a muscular or bone it will get crushed and will leave the shark handicapped and injured.