Tasman prop Ross Geldenhuys was fortunate only to be sinbinned after 10 minutes for a stomp but he did not escape the displeasure of his coach Kieran Keane who refused to send him back on once he served his time.
Eventually Keane had to rescind that decision because of injury 17 minutes from time.
The coach's lesson had little effect as the friction pock-marked an untidy first half which ended on a brighter note when Tasman wing Mitchell Scott scored after being put into space with a terrific pass from Kieron Fonotia.
Before Geldenhuys was dismissed, Tasman No 8 Liam Squire went over after a succession of sweeping moves which eventually left the Bay short of defenders and it seemed the hosts were set for a comfortable victory.
That idea fell over as the Bay showed enormous defensive grit although as Johan Bardoul observed at the interval, that effort would hurt them unless they got some ball and retained it.
Lessons were learned, the niggle abated a touch and flanker Zach Hohneck scored from one Bay raid through the middle of the park to raise the some alarms for the hosts.
Tasman had a lineout and thumping scrum to help their superiority topped by Marty Banks' game craft and goal-kicking but they were untidy in too many areas.
It took a rare and late series of raids for Fonotia to wriggle over and with Banks conversion, make the scrappy game safe for Tasman before loosie Pete Samu scored the bnus point try on the siren.
Tasman 34 (L Squire, M Scott, K Fonotia, P Samu, tries; M Banks 4 con, 2 pen)
Bay of Plenty 13 (Z Hohneck, try; N Evemy; pen, con; D Hollingshead pen) Halftime: 14-3
