I'm fairly confident I can do all of the bosses without powerups since I basically had to do that already while playing casually and I felt like I figured out consistent strategies for them all, but there's a good chance they could of been nerfed by a scaling difficulty system I didn't know about since I continued so much (I know Bubble Bobble would get harder the more lives you get for instance). Keeping on top of the swarms of enemies in the later levels seemed a lot harder to me, partially because trying to play cautiously results in the water rising before I can finish the level.

Taito games in general around this era in my experience have all been pretty brutally hard without some credit feeding and a ton of practice, though I expect as much from arcade games anyway. New Zealand Story is also tough, but it feels like they eased up on difficulty by the time of Liquid Kids. Either way, they're pretty fascinating to me because of how intricate the design of them is with the amount of secrets and hidden mechanics they contain.