Scientists sometimes use very expensive high tech equipment.
This is an Acoustic Doplic Current Profiler which cost $50,000. It is used by hydrologists at NIWA to measure the flow and depth of rivers.  This one was used at Otaki river.  It is capable of taking millions of recordings.  It looks like a bath toy!

The information recevied by the ADCP connects straight to the laptop. Easy! Yahoo for technology!!!