Regarding ecological status assessment with marine benthic macrophytic indicators as per European Water Framework Directive (WFD), linear models are being reviewed (either starting from discontinuous forms or modifying quadratic and algebraic forms). Through use of simple concepts, model flexibility is demonstrated in terms of application to different indicators and varying marine environments. Four variants of the Ecological Evaluation Index (EEI) approach yield similar results (same or adjacent ecological status classifications in 18 out of 20 points) for a Saronikos Gulf data set; they are further compared with variants of the Quality of Rocky Bottoms (CFR) approach over WFD-related aspects (ecological status classification, coverage, richness).