If I’ve learned anything on the DIS, it’s that weddings are very, very regional.
So, for here in the South, a man in dress slacks & a button-down dress shirt w/ a tie, would probably be just fine for a wedding at an aquarium, especially if the wedding is during the warmer months.
Men just don’t wear suits to every event like they used to. And, sometimes, wearing a suit to an event where no one else is wearing a suit is going to make you look out of place or even out of style/not as contemporary.
However, that said, we do have dressier weddings down here too - so it really depends. What time of day is the wedding? Does the invitation specify? Do you know the couple well? Are they more casual or more formal? Have you seen pictures from other weddings at this particular venue?
There are just all kinds of variables when it comes to wedding attire.
My husband & I have been to weddings w/ receptions that were semi-casual, & my husband didn’t wear a suit. We’ve also been to weddings w/ that were more formal, & he did wear a suit.
And the venue doesn’t always matter. He’s worn suits to a wedding reception in a barn & an outdoor wedding reception because they were both more formal events while he didn’t wear a suit to a wedding reception that was in an indoor hall because it was a more casual event.
(I do think it’s a good idea for a man to have a suit though for that occasion where wearing a suit is needed.)