海底かいてい堆積たいせきものじゃありませんでした
kaite ita isekimonojārimasendeshita

Noun
Desu Copula

The polite, past negative form of 海底堆積物

1. It was not seabed sediment.; It wasn't a seabed deposit.

Past/Perfective
Negative
Polite
Terminal Form