They are fine being soaked ... sure they obviously try every nook and corner to find an exit but after a minute or so they calm right down.
Anyways I’m pretty sure all snakes can swim ..plus they can hold their breathe for absolutely ages, apparently.
Anyways I’m not suggesting deep water but certainly more than half their height .
You can use a sealed tub with air holes and cover with a towel to keep them calm .. place on their viv / rub to keep them warm .. for 20 minutes or so ..
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