Да, действительно, 6-й класс допускает только попадание струи воды под любым углом. Ну, это тоже очень неплохо. Если дежурить возле аквариума и достать бинокль сей же миг после того, как он туда будет брошен... Шанс у призм будет

Вот, к слову:
JIS 0 - Without protection
JIS 1 - Drip Proof - Having no harmful influence by dripping of water falling perpendicularly.
JIS 2 - Drip Proof - Having no harmful influence by dripping of water falling from the range covering 15 degrees from perpendicular.
JIS 3 - Spray Proof - Having no harmful influence by rainfall covering the range of 60 degrees from perpendicular.
JIS 4 - Splash Proof - Having no harmful influence by receiving splash of water from any direction.
JIS 5 - Jet Proof - Having no harmful influence by receiving direct jet of water from any direction.
JIS 6 - Watertight - Having no ingress of water into inside by receiving direct jet of water from any direction.
JIS 7 - Immersion Proof - Having no ingress of water into inside when immersed in water under specified conditions.
JIS 8 - Submersible - Always usable when submerged in water of specified pressure.