The Steamers opened the scoring with a Nick McCashin penalty after some good, robust forward play but after a stagnant opening 10 minutes, Trent Renata replied for Waikato.
The Steamers looked lively on attack and their phase play was intense and accurate. The inside backs combination of first five McCashin and Mafi Kefu looked slick and assured, sparking some early Steamers attacks.
McCashin converted another penalty but then crucially missed three kickable efforts to deflate the momentum the Steamers had over a lacklustre Waikato outfit.
Renata tied the scores up at 6-6 before Steamers captain Tanerau Latimer had enough of the missed points and took a quick tap from another penalty close to the posts. The Bay forwards put together some classic driving play and halfback Josh Hall dived over the line for what looked a certain try, until replays showed he failed to ground the ball.
Referee Bryce Lawrence had had enough of Waikato's constant infringing around the rucks and sent first-five Piers Francis to the bin as the first half ended with a scoreline that did not reflect the Steamers' superiority.
Waikato started with far more urgency in the second stanza and Renata put them in front with two early penalties. Down 12-6, the Steamers defended for the first 20 minutes of the half and then broke out with a sparkling attack, started by Lelia Masaga and featuring the loose forward trio, but a dropped pass ended the promising move.
With eight minutes left, Renata had the chance to stretch the lead out past a converted try and he made no mistake from the tee to complete the 15-6 win.
There was to be no magic ending for the Bay, as they ended the second half scoreless and were left pondering all the what-ifs from their dominant first half performance. They face in-form Auckland in Rotorua on Friday night.
Waikato 15 (Trent Renata 5 pens) Bay of Plenty 6 (Nick McCashin 2 pens). Halftime: 6-6.