Dry out Watch SE
Watch SE died during a swim. It won't power on or charge; seems completely dead. Wonder if the seals leaked. Any way to dry it out?
Apple Watch SE, watchOS 9
Apple Watch Series 2 and later can be used for shallow-water activities like swimming in a pool or ocean, but you shouldn't use models other than Apple Watch Ultra or later for diving, water skiing, or other activities involving submersion below shallow depth or high-velocity water.
Water resistance isn't a permanent condition and can diminish over time. Apple Watch can't be rechecked or resealed for water resistance.
I am afraid, at this point, there is not much you can do. See the 'What should I do if my Apple Watch gets wet?' section in:
About Apple Watch water resistance - Apple Support