Get a buy-in from your Dungeon Master
What you are trying to do, is to play a race with all its strength, but avoid its drawback instead of embracing it. That is indeed a common approach¹, and I dare a guess that's why 5e got rid of negative racial modifiers to stats, as they were used with classes for which they didn't matter anyway.
If your DM will decide that getting wet is important to balance out the goodies you got, like water breathing, skill proficiencies, save advantages etc, no matter what game mechanics you will try to use, you will have no guarantees and any DM worth his salt will find ways to make the risk real for you. It will be a problem for you to solve in-game, and you will need to change solutions once in a while. So only way to make sure it won't happen, is to have a deal with DM during session 0.
By the way, if your DM will agree to it, other players may be jaded that you got some goodies for free and they didn't. On the other hand, if risk of drying out will be real for you, it will inconvenience the whole party, not just you. So either way, before playing this race it is a good idea to talk to the fellow players and make sure they are comfortable with whatever solution you and your DM are ready to agree on.
¹ Observation from my experience and from looking at questions on this site.