UPON REHEARING
BURNETT, Judge.After we issued our opinion affirming the jury verdicts, the Idaho Department of Fish and Game petitioned for rehearing. We granted the petition. Counsel for both sides reargued the case and ably responded to numerous questions from the Court. Having examined the factually complex record again, we remain persuaded that the jury verdicts should be upheld.
I
Our analysis rests upon two foundational points. The first is the standard of appellate review. The State would have us hold that the canal company failed to prove it more likely that the canal break resulted from the combined effects of high water and clogging at the trash rack than from the effect of high water alone. We believe the State has confused the canal company’s burden of proof at trial with the *348proper standard of review on appeal. It is true that a plaintiff must show his damage to be the more probable result of a cause for which the defendant is responsible than of a cause for which the defendant is not responsible. Indeed, our principal opinion cites cases so holding. But we do not read those cases to vest in an appellate court the power to decide where the greater weight of probability falls. That remains for a jury to determine. Our function is to decide whether a jury reasonably could have found as did the jury in this case. We will not disturb jury verdicts supported by substantial and competent evidence, even though we entertain doubt as to which party’s version of the conflicting evidence is more probable.
The second critical point is the jury instruction given in this case on proximate cause. Our principal opinion explains how this instruction, to which no one objected at trial, imposed no requirement upon the canal company to prove either that clogging at the trash rack was a “substantial factor” in causing the canal break or that the break would not have occurred “but for” the clogging. Under the instruction given, the canal company was required only to show that the clogging, “in natural and probable sequence ... in combination with” the water flow, caused the canal break. (Emphasis added.) Although we have criticized the jury instruction, it embodies a standard of causation upon which the parties mutually agreed to try the case.
II
Bearing in mind the standard for appellate review of jury findings, and the standard of causation submitted to the jury, we turn again to the evidence. The canal company’s expert in open channel hydraulics testified that if the water depth in the canal had reached 5.3 feet at the trash rack, and if the flow of water in the canal had been approximately 175 c.f.s., the combined effects of the flow and of clogging at the trash rack would have produced an over-topping of the canal bank where the washout occurred. The witness further testified that such clogging would have contributed, in varying degrees, to the upstream water depths at other flow rates as well.
The State has not disputed the scientific methodology underlying this testimony. Rather, the State contends on rehearing that the expert’s opinion was entitled to no weight because it was premised upon facts not in evidence. We disagree — and we note in passing that the State’s capable trial counsel, who has not argued on appeal, never objected on this basis to the witness’ testimony.
The record contains evidence of water depth and flow. As mentioned in our principal opinion, the depth of 5.3 feet at the trash rack was measured by a witness who observed high water marks the morning after the break. His testimony was reasonably consistent with that of another witness who measured high water marks upstream. We are mindful that these measurements seemingly conflicted with the fact that, of the four float-activated gates in the bypass channel, only one was found open after the washout. But we cannot say that the jury was compelled to disbelieve the witnesses’ testimony concerning high water marks. The credibility of witnesses and the weight to be given their testimony are matters exclusively within the province of the jury. E.g., Harper v. Johannesen, 84 Idaho 278, 371 P.2d 842 (1962). A jury is entitled to disregard evidence only if it is inherently improbable. Our Supreme Court has held that “to warrant such action there must exist either a physical impossibility of the evidence being true, or its falsity must be apparent, without any resort to inferences or deductions.” Olsen v. Hawkins, 90 Idaho 28, 37, 408 P.2d 462, 467 (1965), quoting Arundel v. Turk, 16 Cal.App.2d 293, 60 P.2d 486, 488 (1936).
In this case, the observations of high water marks were not physically impossible. The bypass gates had been visually inspected, but not actually tested, shortly before the washout occurred. Moreover, the fact that the gates were 4.3 feet high does not conclusively establish — rather, it *349merely invites an inference — that the water in the canal never reached a depth of 5.3 feet at the trash rack. However, the jury also could have inferred that the combined effects of high water flow and clogging at the trash rack were sufficient to produce a depth of 5.3 feet despite a partial escapement of water over the bypass gates.
The record also contains evidence to support the postulated flow of approximately 175 c.f.s. The principal opinion notes that water from the Salmon River entered the canal by flowing over and around a debris-filled headgate. Witnesses who observed this flow before the washout testified that the water was some eight to twenty inches higher than a “wing wall” extending from the headgate into the river. A written report by the hydraulics expert, admitted into evidence to supplement his testimony, contained an undisputed statement that a twelve-inch flow over the wing wall would have produced a flow of approximately 175 c.f.s. in the canal. The expert also testified, as mentioned above, that even if differing flow rates were postulated, clogging at the trash rack would have contributed in varying degrees to the water depth at the point of the break. We hold that the expert’s opinion was based upon facts in evidence, albeit conflicting in some respects, and was entitled to whatever weight the jury chose to give it.
Ill
Finally, the State argues on rehearing that the verdicts were products of an impermissible “stacking” of inferences. We agree that the jury stacked inferences. Implicitly, the jury inferred from circumstantial evidence that debris clogging the trash rack increased the water depth in the canal and further inferred that this increased depth, when combined with the flow entering the canal, caused the washout. However, we do not agree with the State that such stacking of inferences was impermissible. Again we note, in passing, that the State’s capable trial counsel requested no special jury instruction on this point.
The State now invites attention to Mann v. Safeway Stores, Inc., 95 Idaho 732, 518 P.2d 1194 (1974). In that case our Supreme Court said, “[I]f an inference drawn from circumstantial evidence is to be made the basis of further inference, the first inference must be established to the exclusion of all other reasonable inferences.” Id. at 737, 518 P.2d at 1199. Mann limits, although it does not prohibit, the stacking of inferences. The rigid application of such a limit to civil cases has come under critical scrutiny. See generally 1A J. WIG-MORE, EVIDENCE IN TRIALS AT COMMON LAW § 41 (Tillers Rev.1983). One of the anchor authorities for the Mann rule— and one cited in Mann itself — has been an Arizona Supreme Court decision in New York Life Insurance Co. v. McNeely, 52 Ariz. 181, 79 P.2d 948 (1938). But after McNeely was cited in Mann, the Arizona Court changed direction. In Farm-Aero Service, Inc. v. Henning Produce, Inc., 23 Ariz.App. 239, 532 P.2d 181, 184 (1975), the Court acknowledged that the rule announced in McNeely had created “much criticism and confusion.” The Court stated that even in cases where McNeely had been applied, the courts actually were “concerned with the probative value of the evidence as a whole.” Id.
Nevertheless, even if the Mann-McNeely rule were applied literally to the instant case, we are not convinced that the jury acted improperly. The evidence is undisputed that State employees removing debris before the washout observed the water level above the trash rack to be several inches higher than the level below the trash rack. They further noticed that the differential appeared to diminish as debris was removed. It is also undisputed that the employees departed from the site before all debris had been removed and while more debris was floating down the canal. Finally, it is undisputed that during the evening immediately prior to the washout, a farmer downstream from the trash rack observed the water level at his measuring device to be lower than normal. We think *350the only reasonable inference to be drawn from these undisputed facts is that debris clogged the trash rack to such an extent that it impeded the flow of water, increasing the depth above the trash rack and lowering the depth on the downstream side. Therefore, we find no error, under the Mann-McNeely rule, in the jury’s use of this inference to support a second inference that the increased upstream depth, when combined with the flow entering the canal, produced the washout.
For these reasons we conclude, again, that the jury verdicts should be affirmed.
WALTERS, C.J., concurs. SWANSTROM, J., adheres to the views expressed in his prior, dissenting opinion.