Accurately calculate costs by keeping track of gas fees on different blockchains. Use blockchain explorers to check the average gas price at different times. For example, on Ethereum, gas prices can vary significantly during peak trading hours. Regarding the cost of "farming water" (activities like participating in airdrop - related tasks on platforms), calculate the time and effort spent, and estimate the potential return based on historical airdrop data. Compare the total cost with the expected airdrop value to ensure profitability.