Counterspelled Booming Blade

[Psyren]

Sure, and nothing stops you from running it like this at your table. But there is nothing in RAW that determines it to be like this. And the fact that there are rules that say they work differently in a specific environment (the vacuum of Spelljammer Wildspace) does not allow you to conclude that they also work differently in an entirely different environment, specially when there are rules about those other environments, in the core book none the less, that don't mention such differences.

The default rule is that the spell does what it says it does when you cast it. The burden of proof is on you to find a rule that says being underwater changes that, especially since the only printed effect being underwater actually has is resistance to the fire damage it produces.

And I'd really like someone to address my argument about Lesser Restoration and Blinding Smite, and if you agree that Lesser Restoration indeed cures the Blindness of the Blinding Smite even without addressing the spell specifically why does the Tidal Wave extinguishing unprotected flames does not extinguish the unprotected flames of Wall of Fire, just because it does not address the spell specifically.

Lesser Restoration specifically ends the condition so that's what I'd go with.