Have you ever tried crayfish? Гурманы (Connoisseurs) say that they are especially tasty during the months in which a R is used, which means from September to April. Но именно эти месяцы в России являются традиционно холодными, (but these months are traditionally cold, especially in Russia), and crayfishes hide in water holes.
To find them during this period and pull them out of the hole, one has to spend a long time in the freezing water. Мало кто согласится на такую работу по доброй воле (rare are those who would accept to do that job willingly). In ancient times, landlords had to force their peasants to go and get them, and peasants would receive this order as a real punishment.
That's why the expression “я тебе покажу, где раки зимуют” (I'll show you where the crayfishes hide) was a serious threat and is still used when you want to force someone to do something he or she doesn't want to do.
“Пошло насмарку” (For nothing). This expression can be used when you are upset about someone who has done a job that didn't bring the expected result, when this job was done in vain, when someone just просто испортил всё (messed up everything he has done).
The word “смарка” in modern language is found only in this expression, but в разговорном русском языке (in colloquial Russian), you can find other words with that root “марать-замарать” (to soil, to stain). For example “Это – человек недостойный, я не буду его наказывать, не хочу марать об него руки” (he is an unworthy man, I will not punish him, I don't want to dirty my hands on him) or “Своим недостойным поступком он замарал честное имя своих родителей” (With his dishonourable behaviour, he brought disgrace on his parents' name).
Scientists say that in the past the verb “смарывать” (to clean off) was used in Russian. On this basis, it becomes clear that the expression “пойти насмарку” means “быть стёртым” (to be cleaned off, to be erased), “уничтоженным бесследно” (to be destroyed completely).