*77 MEMORANDUM *

Naaman Shepard (Shepard) appeals the district court’s judgment following a bench trial that the marine insurance policy issued by Foremost Insurance Company (Foremost) did not cover his loss.

1. The Washington proximate cause rule, see Wright v. Safeco Ins. Co. of Am., 124 Wash.App. 268, 273-74, 109 P.3d 1 (Wash.Ct.App. 2004), and the federal proximate cause rule, see Commodities Reserve Co. v. St. Paul Fire & Marine Ins. Co., 879 F.2d 640, 643 (9th Cir. 1989), are substantially similar. Therefore, any error in applying the Washington law was harmless. See Coutee v. Barington Capital Group, L.P., 336 F.3d 1128, 1134-35 (9th Cir. 2003) (applying harmless error to a choice of law decision).

2. The policy exclusion for “lack of reasonable care or due diligence in the maintenance of your watercraft” is unambiguous and must be enforced. See Conrad v. Ace Prop. & Cas. Ins. Co., 532 F.3d 1000, 1005 (9th Cir. 2008).

3. The district court did not clearly err in finding that the efficient proximate cause of the loss was a lack of reasonable and proper maintenance because trial testimony supports the finding. See Exxon Co. v. Sofec, Inc., 54 F.3d 570, 576 (9th Cir. 1995).

4. Shepard’s reliance on Founders’ Ins. Co. v. Rogers, 305 F.2d 944 (9th Cir. 1962) is inapt. Rogers was decided under English law and a policy provision providing that the vessel owner discharged his responsibility under the policy by delegating the maintenance responsibility to the master. See id. at 945.

AFFIRMED.