The Sea Lion was an important kayak in the mass production aspect and getting people into the water without having to make their own boat, or having to purchase a more expensive fiberglass kayak.
It has been about six or seven years (maybe more) since it was produced. The plastic ones are very old now, not suitable for putting stress on the plastic. If you find one and want to use it for calm water, it will work. If it is in a reasonable price range (under $300), then it may be a good purchase, but anything over that is excessive.
Good boat for learning in calm water, handles well, lots of stability. Not suitable in plastic for rough water or any situation where the kayak can be stressed. The plastic breaks down over time and these, along with Narpas, Kyooks, Chinooks, etc. are ready to be put out to pasture.
Spend a few bucks more and find a newer boat.