don't know if we already have this but cap 15 is a lagoon in honolulu. on the left of the lagoon is the ala moana bech park and to the right is the hawaii yacht club next to the hilton hotel

Yep, you got it, Ala Wai Yacht Harbor.
I was double checking to make sure we had all the identifiable Hawaiian caps nailed down, and I just noticed this one, which you had already figured out. If the angle was a bit different, you could see my high school, but it was the
last cap I recognized.