潜水刀

dive knife

to dive / to go under water / (in an online forum) to lurk

hidden / secret / latent / to hide / to conceal / to submerge / to dive

surname Shui

water / river / liquid / beverage / additional charges or income / (of clothes) classifier for number of washes

knife / blade / single-edged sword / cutlass / CL:把[ba3] / (slang) dollar (loanword) / classifier for sets of one hundred sheets (of paper) / classifier for knife cuts or stabs