Those giant crayfish in the lakes are a real pain, especially with that crazy long-range spit attack they do. Honestly your best bet is to just zoom past them on torrent whenever you can, since fighting them rarely gets you anything worthwhile. I usually stick to the higher ground around the edges of the lake, makes it way easier to avoid them altogether.

If you absolutely have to deal with them though, i've found that sleep arrows work surprisingly well - just two shots and theyll take a nice nap. Sometimes i hide behind those old ruins and statues scattered around, particularly that gazebo near the fallen ruins which is pretty handy for cover. The crustaceans cant break it so you can safely plan your next move.

Something interesting i discovered is that they're actually really vulnerable if you can get under them and hit their belly, especially with upward attacks. But honestly, unless you really need those smithing stones from the red-eyed ones, i wouldn't bother fighting them at all. Just unlock the nearby sites of grace, and use those for quick getaways when things get dicey. The underground roadside grace is particularly useful if youre trying to grab some loot without dealing with these oversized seafood platters.