When the Baltic Dry Index (BDIY), a measure of daily charter rates to ship a variety of commodities across the globe, moves higher, ETF investors get excited about the Guggenheim Shipping ETF (NYSEArca: SEA).

On the surface, the relationship appears to make sense, but the reality is SEA is not a dry bulk shipping ETF. SEA tracks the Dow Jones Global Shipping Index. That index is a collection of dividend-paying global shipping firms, not all of which are focused explicitly on the transport of dry bulk commodities.

SEA holds 27 stocks and that group does NOT include day trader favorites such as DryShips (NasdaqGM: DRYS), Baltic Trading (NYSE: BALT), Diana Shipping (NYSE: DSX) and related fare. So while SEA is the ETF some investors turn to in an effort to express a view on the Baltic Dry Index, the fund provides little leverage to that index.

Still, SEA’s association with the Baltic Dry Index has been enough to drive the ETF higher by almost 7% in the past month. That time is particularly useful for examining the relationship between SEA and the Baltic Dry Index (or lack thereof). As the chart below shows, the Baltic Dry Index has plunged over the last several weeks. SEA has not and the ETF is mere pennies away from its 52-week high.

There is an index SEA investors should follow, that being the Baltic Dirty Tanker Index (BIDY). The index aggregates rates from major trade routes every day and is a good indicator of overall shipping rates hired to move crude oil, according to Market Realist.

Companies such as Frontline (NYSE: FRO), Nordic American Tanker (NYSE: NAT) and Teekay Tankers (NYSE: TNK) are among the investable crude tanker names. Nordic American and Frontline combine for 5.5% of SEA’s weight.

SEA’s largest holding is Denmark’s A.P. Moller – Maersk, which operates across multiple businesses, not just shipping. The company had $59 billion in revenue in 2012. SEA is also home to Teekay LNG Partners (NYSE: TGP), a shipper of liquefied natural gas, and Teekay LNG Partners (NYSE: TOO), a provider of offshore oil storage services.

Bottom line: There is a perception that SEA is the “Baltic Dry Index ETF.” The reality is that is not true and the chart above shows sometimes that is a good thing.