Semi-aquatic (webbed feet, streamlined body, eyes and nostrils on top of head, flattened tail), muscular flaps to seal off orifices when diving, flap over throat so they can catch stuff underwater without drowning, jaws adapted for grabbing and crushing prey (huge bite force), transparent protective membrane covers eyes when diving/catching prey, stomach can basically break down everything (iron stomach) because they're not fussy eaters; body armour