Even if this card is destroyed during the resolution of a Chain, you can activate its effect after the Chain finishes resolving. It does not “miss the timing.
You cannot activate this effect if you have no Level 4 or lower WATER monsters in your Deck.
If your opponent controls your “Shark Cruiser” and destroys it with a card effect you cannot activate the effect of “Shark Cruiser.”
Tips, related cards, skills
A legendary Ocean
With "A Legendary Ocean", this card's Level is reduced to 4, so it can be Normal Summoned without Tribute.
As suggested by its appearance and relation to "Orca Mega-Fortress of Darkness", you could use this card's effect to summon 1 of each (or 2 of 1) a "Cannonball Spear Shellfish" or "Torpedo Fish" to be used by the effect of "Orca"