We were just having this conversation because my spouse and I are also heading to Galapagos in January for a liveaboard. In the past, I've carried tip money (for two) and other cash in three places. I wear light weight hiking pants on travel day and use the zippered pocket for the $100s. The pockets are long enough for the money to lay flat. Use a different pocket for the $20 and split the rest between my wallet and my spouses' wallet. Weird, yes, but I know where it is and the zipper is a great deterrent to pickpockets. In hotels prior to boarding the boat, we use the in-room safe or, if no safe and feeling a bit at risk, the hotel safe. The only time we've been robbed was at a dive resort with a broken safe. Our whole group of 14 got hit by the "cleaning gang". They took between 20 to 40% of the cash we each had in our rooms. I guess they hoped we wouldn't notice.
Anyway, for transit, try pants with long, zippered pockets.