Hmmm you see I don't know much about shark or water monster that much except ice bArriers
Then since you have instant fusion why put some heros in the extra like absolute zero and what ever level 5 hero then put some heros in main deck and add miracle fusion and put cards that can send cards from deck to grave or hand to grave to get that fusion also put some cards that
Can bring banish cards to the field.
It may not be a shark deck but can be a
Jaden shark xyz deck