This isn't much to do with fighting ocean crawlers as it is about killing them and hitting them. I find killing and slashing skeletons to be very therapeutic, like when you sword dash through a large group and you get those crunchy sound effects, the stunning and stammering of the enemies and the bone pieces flying off them as they die.
For Ocean Crawlers this seems to be quite the opposite. When you hit an ocean crawler you get a very muted sound effect (most notably on the crab) and your attacks feel weak as a result. You don't get any fancy VFX when making contact with them or satisfying sounds. I've found some of those sounds akin to slashing at cloth textures like that of a ship carpet. You take a swing at an ocean crawler and you don't get the feedback that you do with skeletons, it feels unsatisfying. To add to that, skeletons would violently explode upon killing and make a rattling and crashing sound, whereas Ocean Crawlers let out small shrieks while they have a heart attack or fall on their faces before waiting to turn into smoke. It makes you feel like you've defeated something more powerful, sure, but it (and this might be a more personal take) feels lifeless in terms of audio/visual feedback.
I think to combat this, if there were more VFX/Particles for swings and sounds for attacks (like you would imagine hitting and cracking shells would be) it would be small but effective. As for the deaths.. I don't know if there's much to help with that, though often it feels a bit hard to tell when one dies without looking at it. A better sound effect feels like it could go a long way.
This is just from my experience with them and their ingame feedback to getting attacked. I could be overthinking this, but to me personally it feels rather unsatisfying to land a hit. Gunplay is a different story, I'm the idiot that sword slashes every ocean crawler.
