Working at Port of Itajai, Santa Catarina, Brazil. Jan. 29th, 2005.
It seems to be a tug. But it's not. Iguazú is a "Specialised Carrier", registred as SubType "Dredger/Suction".
As far as I could go with my researchs, it's a Water Injection Dredger, owned by Ballast Ham Dredging (dredging depth of 27 meters).
IMO No: 9201920
Built: 1999 by Harlingen
GT: 478
NT: 143
Class: BV
Draft: 3.00
LOA: 43.60
Beam: 10.00
Flag: Panama (since 06/23/2003; formerly Netherlands)