Benjamin, if the engine turns then it would be worth restoring, you may need new coil, points and condenser for the magneto if water has got in. First job would be to remove flywheel then strip and clean magneto, especially areas such as where coil attaches to back plate. Then reassemble, set points and fit flywheel so you can spin it over to see if you get a spark.
If engine is seized then it will be more work.