In trading on Monday, shares of the Guggenheim Shipping ETF ( SEA) entered into oversold territory, changing hands as low as $18.88 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of Guggenheim Shipping, the RSI reading has hit 28.0 — by comparison, the RSI reading for the S&P 500 is currently 41.8. A bullish investor could look at SEA's 28.0 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), SEA's low point in its 52 week range is $17.45 per share, with $23.13 as the 52 week high point — that compares with a last trade of $18.86. Guggenheim Shipping shares are currently trading off about 1.5% on the day.