dissenting:

The crucial issue before us is whether, in the circumstances of this case, reasonable minds can differ that wake jumping is openly and obviously dangerous. Because the obviousness of the dangers of wake jumping depends on the factual circumstances and because this case is rife with disputed issues of material fact, summary judgment was not appropriate.

On July 31, 1999, two eighteen-year-old friends, Matthew McAlpine and Mason Hodges, rented Sea Doo personal water-crafts 2 (“PWC”) from Summer Fun Rentals (“Summer Fun”) on the Columbia River. It is undisputed that neither Hodges nor McAlpine had ever used a PWC. Summer Fun’s employee gave them brief instruction relating to the “kill switch” feature and the location of the throttle. Summer Fun also told them to stay out of shallow water and to “stay below 5 miles an hour until they hit the buoy ... [and then to] ‘go ahead and do whatever [they] wanted to do.’ ” Summer Fun did not tell Hodges and McAlpine that wake jumping can be dangerous. 3 Hodges and McAl-pine thought wake jumping was permitted because they “saw others doing it” and because McAlpine “had previously seen people jumping wakes while operating personal watercraft on television.” Hodges and McAlpine rode the PWC without incident for about fifty minutes, during which time they executed spinning and wake jumping moves. Up to this point, the facts are clear.

McAlpine then saw a boat described as a “pleasure craft” coming towards them. He and Hodges decided to pass the boat on opposite sides so that they could jump its wake. We do not know how fast the pleasure craft was going or how large a wake it created. It appears that, in the act of jumping the wake, Hodges fell off of his PWC in McAlpine’s line of travel, resulting in a crash. Hodges was severely injured, resulting in the amputation of his leg below the knee. Hodges filed this negligence action against Summer Fun, alleging that Summer Fun had a duty to warn of the hazards of wake jumping.

As the district court observed, “[t]he facts in this case are disputed.” The district court noted that Hodges “cannot remember the exact details of the accident.” McAlpine apparently could not see how Hodges ended up in his line of travel and did not see Hodges before hitting him. We do not know how big the wake was, the size of the boat that created the wake, the amount of boat traffic on the Columbia River, the wind conditions, the water current conditions, and any other facts that might have contributed to the accident. The truth is, we know very little about what happened that day.

Hodges tried to inform the court’s understanding of the accident by presenting *93 reports containing expert testimony on the operation of the PWC and the manner in which the accident likely occurred. One expert’s report expressed the opinion that “reasonable care ... requires that a PWC rental agency provide training prior to allowing anyone to rent the PWC.” Another report expressed the belief that “the principal cause of the collision ... was the entrusting of the two vessels to operators who had neither the skills nor the training necessary to operate them safely.”

The district court disregarded the expert testimony “with regard to the reconstruction of the accident” because the court found that the testimony was “lacking in evidentiary support” and “speculative.” 4 The court brushed aside the “equally plausible” opinions of Hodges’s experts as to how the accident in fact happened. The district court instead found neither version “more probable” than “any other plausible explanation” and thus supplanted the experts’ version of the accident with its own. The district court then granted summary judgment, even though it had acknowledged that “[t]he facts in this case are disputed.”

Summary judgment can only be entered if “there is no genuine issue as to any material fact.” Fed. R. Civ. P. 56(c). Reviewing a district court’s grant of summary judgment, we view all evidence in the light most favorable to the nonmovant. See Gulf USA Corp. v. Fed. Ins. Co., 259 F.3d 1049, 1056 (9th Cir.2001). We have reversed summary judgment in many negligence cases involving a duty-to-wam theory of liability because the factual record was insufficiently developed. See, e.g., Butler v. Ingalls Shipbuilding, Inc., 89 F.3d 582, 586 (9th Cir.1996) (reversing because genuine issue of fact remained as to whether specifications of contract conflicted with contractor’s duty to warn); Cook v. Exxon Shipping Co., 762 F.2d 750 (9th Cir.1985) (finding triable issue of fact as to whether Exxon failed to warn plaintiff of hidden danger on vessel because “a trier of fact could reasonably find on the basis of this evidence that Exxon breached its duty to warn”); Graves v. U.S. Coast Guard, 692 F.2d 71 (9th Cir.1982) (reversing summary judgment because disputed factual issues remained regarding inherent dangerousness and whether warnings addressing danger should have been posted); Rookard v. Mexicoach, 680 F.2d 1257 (9th Cir.1982) (finding triable issue of fact whether bus line had duty to warn passengers of poor safety record of foreign bus line and of Mexican statute of limitations for tort actions). The instant case also presents a controversy where disputes of material fact should have precluded summary judgment.

The district court should have developed the factual record relating to the accident because the facts are crucial to determining whether the wake jumping in this case was obviously dangerous. Some wake jumping is dangerous and some is not. Washington law makes it a misdemeanor to “recklessly jump[ ] the wake of another vessel unreasonably or unnecessarily close to the vessel or when visibility around the vessel is obstructed.” Wash. Rev. Code § 79A.60.190(5), (8). By not prohibiting *94 wake jumping outright, the law recognizes that non-reckless wake jumping is lawful. To understand whether Hodges and McAl-pine were engaged in activities that were obviously dangerous, we have to know the facts.

The Second Circuit came to a similar conclusion in Martell v. Boardwalk Enterprises, Inc., 748 F.2d 740 (2d Cir.1984). In that case, Martell was operating a jet ski that was hit by a motor boat. See id. at 744 . The boat’s impact severed the lower two-thirds of Martell’s left arm. See id. at 745 . In determining whether the manufacturer of the jet ski had a duty to warn operators of the dangers of jet ski use, the Second Circuit found relevant that Martell “had never operated a Jet Ski before the day of the accident,” that “boat traffic was heavy, causing waves and choppiness on the water, with some chops as much as two feet high,” “that the Jet Ski did not handle well in rough or choppy water conditions,” and “that the small size and low profile of the Jet Ski tended to hinder its visibility to other watercraft, and that the choppiness of the water on August 81 further tended to obscure the Jet Ski from view.” Id. at 744-45 . Bearing in mind all of the detailed factual circumstances, the court concluded that, “[vjiewing the evidence in the light most favorable to the plaintiff ... reasonable jurors could conclude that Kawasaki breached a duty to warn of potential dangers associated with foreseeable uses of the Jet SM.” Id. at 747 .

Like the Second Circuit in Martell , we must know all of the details surrounding the accident to determine whether the dangers of wake jumping in this case were open and obvious. Here, the district court dismissed relevant expert testimony, improperly made findings that should have been reserved to the trier of fact, and prematurely granted summary judgment despite the existence of disputed issues of material fact. Because those factual issues are critical to the outcome of this case, the district court’s grant of summary judgment in favor of Summer Fun Rentals must be reversed.

. A Sea Doo is similar to a wave runner or a jet ski.

. The record shows that the manufacturer of the PWC in question, Sea Doo, provides materials to buyers that counsels users to "[ajvoid wake jumping.” The National Association of State Boating Law Administrators produces a model PWC Renter Orientation that tells users, "Do not jump wakes or waves.” The Personal Watercraft Industry Association tells riders to "[a]void wake jumping.” In spite of these warnings, Summer Fun did not tell Hodges and McAlpine to avoid wake jumping. A conscientious rental agency would make this information known to its renters.

. The district court provides scant support for its conclusion that the expert testimony is speculative. The district court says that one expert failed to "cite to the record to support his conclusion that [Hodges] and McAlpine had neither the skills nor the training” to operate the PWC. We know, however, that neither Hodges nor McAlpine had ever operated a PWC before. The court also questioned whether Hodges was actually "jumping wakes at the time he lost control.” Both the physical circumstances surrounding the accident and the testimony of eye witnesses make clear that Hodges fell into the water after jumping a wake.