Clank!: Sunken Treasures

Yes — SCUBA is a Market item placed with the other Market items and costs 7 gold; it is worth 5 points at game end, prevents the 1 damage for ending your turn in a flooded room, and reduces the Boots cost to move through flooded tunnels from 2 to 1 (pp. 1–2).

You must enter a non-flooded room at some point during your turn or you take 1 point of damage at the end of your turn (you avoid this damage if you have SCUBA); if you have no Clank! cubes and must take damage, you are knocked out (p. 2).

No — moving through a Clank! tunnel normally adds Clank! cubes equal to the icons, but you do not add Clank! when you teleport along those passages (p. 2).

Those effects trigger only when you discard the card during your turn (for example to pay a cost or via a card effect); they do not trigger when you place cards into your discard pile at the end of your turn or when you first acquire a card by skill (p. 2).

The Goldfish is placed in Reserve and is not discarded when defeated; each player may fight the Goldfish and/or the Goblin multiple times each turn and earn its reward each time (p. 1).

Yes — when you enter a room that has a gold icon you gain the amount of gold shown (p. 2).