I need help diving

[crystal light]

I'm stuck diving. I circled where I still have black roots. And in the top left corner I can't go through and it looks unfinished, the map shows an area, so I'm not sure if I should be able to get there. Please help me out, thanks!

[bronze lintel]

You can go down further left where I circled left. It is hard to find because they are not regular stakrs but orange coral stairs

*where I circeled red