Requesting my necromancer Rien during a beach episode, summoning a tentacle monster from the depths to unleash upon would-be heroes, only to lose control of it and be its first victim.
She should be wearing a suitably evil and elegant swimsuit, and a large hat or magic sunshade (her skin doesn't tan, it burn when exposed to the sun). If you just want to draw a sexy pinup in a swimsuit that's fine too.
Alternatively, the tentacles could grab others OC if peoples feel like joining in.