That odd looking yellow submarine is the Wild symbol, appearing only on reels 1, 2, 4 and 5, and substitutes for other symbols except for the '20000 Leagues' symbol. This is another example of a totally dumb Wild symbol that doesn't pay for itself, it doesn't double any wins, nor does it become stacked or expanded. Very disappointing indeed. The logo '20000 Leagues' is a special Wild symbol that appears only on reel 3, but is no different from the Submarine Wild symbol in being very dumb. There aren't any Scatters in this game, losing even more chances of making additional wins, but a Free Spins game can be triggered whenever a Submarine appears with the '20000 Leagues'. Each appearing submarine awards 10 free spins, with all wins doubled, and more free spins can be retriggered.
As far as I have played this game, I have only gotten 1 submarine with that 20000 Leagues symbol, for 10 free spins. Have never got 2 or more submarines to trigger 20 or more free spins, which was frustrating. However, retriggering of the Free Spins game do happen quite often, giving 20 free spins in total , or sometimes 30, but I've never gotten more than that. As for the symbols in the game, the Captain pays 5000x, the Diver pays 2000x, the Shark pays 1000x and the rest pay from 1000x down to 150x, all per line bet for 5 of each kind. A low paytable.