'baptised into Moses' - does it says baptism is required for salvation

1 Cor 10: Paul is talking figuratively here. To render it literally would make 'baptized into Moses' mean 'immersed into Moses' which doesnt make sense. 'baptized into Moses' means 'identified with Moses'. Moses here represents Christ and the spiritual drink represents the Holy Spirit.
So all that Paul is trying to say is that even though you Corinthians, as christians identify with Christ and have received his Spirit, dont grumble and whine at God just as the Israelites did, lest you meet the same fate as they did.
Note that the Israelites were already called Gods people when God talked to Moses throught the burning bush. The sea never touched them and going through the red sea never changed their relationship with God.