For large portions of the encounter at Cresswell Park, Claremont shaded its opposition.
However, when the Mariners needed it, they dug deep to find something that would keep them in the game with the bat in the first week and with the ball on Saturday.
Simmons backed up his 160 runs, with three wickets, the last two sealing the 10-match points for Rockingham-Mandurah.
The supporting cameos came throughout the pulsating contest.
Josh Smith (48), Aidan Andrews (2-48 from 22 overs) and Brendon Diamanti (2-14 off 12 overs) all chipped in, just as the Tigers gained the upper hand. Shielding last week’s 278, the Mariners made timely inroads with the Tigers comfortable at 2-126.
None of their batsmen made half-centuries but wickets were the only thing that would see the Mariners home.
At 7-262 and with a 46-run eight-wicket stand going, the home side again looked likely but a run out and two Simmons wickets saw Claremont-Nedlands dismissed for 271.
Third grade is the only team with four wins in the league, as it made easy meat of Claremont’s 114. Alex Whiteman steered the team home with 67 as the Mariners held a 47-run first innings lead after scoring 161.
This left the bowlers with time to carve through the home side again in the hope of an outright result.
Claremont-Nedlands survived narrowly and were 9-92 in the second dig as the Mariners feasted on the Tiger carcass.
At Lark Hill, heavy losses were taken by second and fourth grade, both teams still searching for wins this year.
Seconds found a winning target of 320 too steep and lost the top order early.
Brad Ranford (48), Tom Lewis (32) and Jamie Ryan (31) punched on to add some respectability before being the innings ended on 192.
The fours only had 130 runs to play with and Claremont-Nedlands closed the day’s play at 7-279.
Rockingham-Mandurah’s under-17s side had a day out taking rare outright points.
They dismissed Claremont for just 32 and 24 in 35 overs of play.
Aaron Burrage took six wickets, including a second-innings hat-trick and Jordan Brokate had first-innings figures of 4-2 to end with six scalps for the match.
The colts confirmed the talent flowing through the club with a solid win against Mt Lawley in the first of three qualifying colts’ matches. Half centuries to Elliott Lyons (53), Jake Eardley-Wilmot (59) and Jacob Rodgers (67) helped the Mariners to 3-226.
In reply, Mt Lawley made 9-219 as Stefan Botha’s 5-36, his second bag in a fortnight, helped the under-21s through.