In trading on Friday, shares of the Guggenheim Shipping ETF ( SEA) entered into oversold territory, changing hands as low as $21.48 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 29.0 — by comparison, the RSI reading for the S&P 500 is currently 34.3. A bullish investor could look at SEA's 29.0 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 $17.94 per share, with $23.32 as the 52 week high point — that compares with a last trade of $21.62. Guggenheim Shipping shares are currently trading off about 0.7% on the day.