Living by the Ocean it´s a normal circumstance. Simple Casios, Timex & alikes I´ve always used otb in, around and under water without any problem. I just don´t touch the pushers when submerged. Reps need silicon-greasing of the caseback gasket and tightening of the caseback (almost always) with the respective tool (cheap). A bit of silcon grease on the screw-in-crown (You can carefully work around it with a toothpick) is also recommended. It´s been a lot of uncomplicated and "careless" fun and variety, the total cost of the rep is less than changing the gaskets and depth-testing of an expensive gen with a precious movement inside.
Not all reps are suited, simple divers without HE-escape-valve are best. The ones I use for swimming/snorkelling are chosen for a TD-rating to 100m (at least 50m) or "waterproofed from factory" which doesn´t mean anything, but I´ve only had good experiences with the eight reps I do use in cold water for several years by now (after above treatment). No hot showers and steam because of the expansion/contraction of gaskets and metal tolerances in reps. All other reps I keep quite far from water
To be on the safe side a waterresistance test is recommended, even the simplest one to just 30m will do for playing around. Around crystals You might use UV-glue but that´s already going too far 4me, than I simply wouldn´t use it. For scuba-diving I´ll take certified gens only.