can you tell what side of the engine its coming from, does it act like its missing, thats loud for a rocker,

Does not act like it's missing. Has no difficulty staying running at a steady rpm. I haven't really been able to localize which side it's coming from. I'll go fire it up again and report back.

Seems to be loudest on the Stbd side, towards the rear. Really seems to be much too loud to be a rocker or valvetrain noise, at least not like any I've ever heard. Engine has no trouble staying running at idle.

Pull the plugs to see if any show damage?
Maybe get a look with a bore scope.

...........

Bent pushrod which made rocker arm come off of it. But my iphone7 is no hi fidelity sound system.

Pull valve cover. If you find rocker off ck for broken valve spring too.
Maybe lifter also. This you can check with new pushrod if you need new pushrod.

It costs nothing to look but continued running could result in big $$$$$ in my humble opinion. I'm thinking a bit deeper than a rocker arm or push rod but the movement of either may indicate a problem with a valve or seat. Obviously something water ingesting related going on presuming that's when the noise started.

Don’t get out of boating just for a small tapping noise,it’s probably a easy fix.

Pulled plugs. Cyl 5 appears to have its ground electrode pushed in towards the center electrode. All others appear normal albeit a bit rich.

Was 5 one that had high leakage?
Something dancing around in there.
Bore scope?