You cast your hook into the ocean in order to harvest fish and treasure. But the fish are not bassic creatures, they will not be harvested withtrout putting up a fight. As a wise man once said: "The best defense is a lot of bullets". Looking at the behaviour of the fish, they seem to have writ this quote into the very bedrock of their culture, if their determination to krill you is any indication.
Whale you descend through each level you have the opportunity to swell your coffers like a pufferfish, by grabbing treasure and harvesting fish. But of course this must be considered against the risk of damage that may be inherent to attacking these aquatic adversaries and seeking these submurged shinies. Maybe it is best to battle anemone for monetary reward. Or perhaps it is a difficult situation beyond your equipment that you should not fall for: hook, line or sinker.
Among the underwater world are items for you to find and wield. Some of them you will find offered up to you for free on a silver platter as though you're not a fisherman but a nobleman in an esteemed restaurant. Others will require payment, for there are some in this world who understand that everything is worth some fee. As your skill waxes you will find ways to coral ever more items into your item purse, amassing an uncodly amount of power.
If your hook is slain, the voyage begins anew, with nothing taken from one run to the next other than your own expertise and knowledge. Your mind attunad to the ways of the game, learning how to maximise your power and wealth via items, how to skate around the bullets of the fish to stay unharmed. Different enemy patterns and items will appear on each run, so your ability to improvise will be tried.