Of those, I'd take the Tuna as it is the more unique of the three. If these were mine and I was only taking one, it would be the PO but, as you are taking the Sub ND, I'd go with the Tuna.
BTW, I would not snorkel or dive with any of them on anything other than a one piece nylon strap, NATO, ZULU, etc. I'm in the bad luck club that lost a watch due to what I have to assume was a spring bar failure. I'm usually a bracelet guy but in water of which I cannot see the bottom, it's nylon for me.
Enjoy your trip.