There are a heap of polls this spring, here is a very brief primer on what is going on:
ACRA*: run by the coaches of the American Collegiate Rowing Association (ACRA), this is a coaches poll done weekly by polling all participating institutions
cMax: based on a well-known statistical technique called OLS (ordinary least squares), cMax ranks the likely finish order as well as a unique 'seconds back' prediction; you can read the full the methodology linked at the top of each week's poll; run by Chris Maxwell and Andrew Kirk
EARC Heavyweight Men*: run by the coaches of the Eastern Association of Rowing Colleges (EARC), this is a coaches poll done weekly by polling all participating institutions
IRA Coaches Poll*: run by the administrators of the IRA, this is a coaches poll done weekly by polling all member institutions
IRCA Coaches Poll: run by the members of the Intercollegiate Rowing Coaches Association (IRCA) of men's rowing programs, this is a ranking done weekly by polling all member institutions that includes the of D1, D3, and Lightweight Varsity Eights
Pocock CRCA Poll: run by the members of the Collegiate Rowing Coaches Association (CRCA), this is a membership poll done weekly by polling all member institutions
rankOar: a new ranking that uses the Plackett-Luce Choice Axiom to simulate each rowing race thousands of times; you can read the full the methodology linked at the top of each week's poll; run by Nate Carmody and Curt Hastings
Sprints League Women's Poll*: including institutions entering the annual Women's Sprints and run by IRA administrators, this is a coaches poll done weekly by polling all entered institutions.
* designates that the poll is used to select and seed the corresponding championship