According to scientists consensus, there is no place in the ocean without plastic pollution.
Here are two exaples of excepcional records of acummulation of deep-sea litter in the Japan Trench. Plastic bags in the gap made by a big earthquake off Sanriku in Shinkai, at 6272 m depth (picture a) and the Suruga Bay at 2170 m (in the picture b).
These two records come from a research dive done in 1991 by JAMSTEC.