One important difference: salt-water animals (including crustaceans) harbor parasites which are less compatible with humans, for them humans are dead-end, they can't close the complex reproduction cycle. Land insects and fresh-water crustaceans (e.g. crayfish) are much more dangerous for humans. Lobster sashimi is much safer than eating a raw crayfish from a river or lake. The latter can cause a serious lungs disease.

> if you eat fresh produce from your garden, there are likely to come some small critters along with that.

I once found a caterpillar inside an eggplant ;)