Seadoo sells a "storage oil" in an aerosol can, with an attachable straw that you can stick into the rubber nipple in the top of the air intake (depending on model.).
Academy also sells a "storage oil" under Sta-bil's name, and I used that this year.
Basically, just a thick lube in an aerosol can (seems kinda like lithium based, but not sure) that you can spray into the running engine and coat all the carb, intake, and exhaust components to sit for the winter.
Then you usually squirt into each spark plug hole for about 15 seconds each, roll over the engine (by hand or a quick tap on the starter) for just a couple of revs, and put the plugs back in and wait til spring.
It will smoke for the first 5 minutes of running when you start it up in the spring. You may also need to remove the spark plugs and put a rag over the spark plug holes and hit "start" and let the pistons spray the excess lube out the top into the rag. Then reinsert the plugs and start it. Either way, lots of smoke for a few minutes. But the engine isn't seized up.