This wasp dives underwater to attack moth larvae.
In recent years there have been a few new discoveries of normally terrestrial or arboreal arthropods that are somewhat amphibious, such as Scolopendra cataracta, a large centipede from Laos that swims to escape danger (and maybe hunts underwater).
And, of course, the Diving Bell Spider, Argyroneta aquatica, is a well known spider that crosses the air/water boundary.
Anyone have any other interesting arthropods (insect type, not crustacean type - eg: crabs, shrimp, etc) that make that land/water transition as adults?
Microgaster godzilla - https://www.science20.com/news_staff/microgaster_godzilla_new_species_of_wasp_dives_underwater_to_attack_a_caterpillar_host_video-251563
Scolopendra cataracta - https://www.nationalgeographic.com/news/2016/06/amphibious-centipede-discovered-laos-scolopendra-cataracta-new-species/
Argyroneta aquatica - https://animaldiversity.org/accounts/Argyroneta_aquatica/