One of Cousteau's divers had an octopus that he was playing with wrap itself over his twin hose valve (the valve itself, not the mouthpiece) and by creating a suction, prevented the diver from breathing in. This caused much hilarity amongst his fellow divers.
Got quite some problems with a angry octopus last year. Or really no problem, as the octo was about 4cm long.... But he tried to kill me with his ink mg: hehe! Funny creatures, eager to see some bigger ones of them.