If you're concerned about marine life the most significant thing most people can do is go vegan. Run off from cattle farms, crops grown to feed or "finishʾ cattle, fish farms and fishing are completely and utterly devastating.

If you want serious sun protection the pasty metallic ones (sometimes marketed as mineral sunscreen) that aren't invisible/nanoparticle stuff work great, are seemingly less bad for marine life, and because you can actually see them you can tell when they need reapplying because you've wiped some off.

Most people don't want to look like they're getting even for blackface's sake though. Nanoparticle sunscreen might not be as bad as some organics but I am extremely warey of anything long lived that bioaccumulates given our amazing track record.

So if you want a balance between not looking stupid and probably not singlehandedly causing bleaching events (again it's negligible next to not deliberately killing stuff in the ocean and the carbon emissions of carnism) then organic sunscreens that avoid the ingredients banned in Hawaii (oxybenzone and octinoxate) don't seem too bad (it's also understudied though, and results in petri dishes aren't always applicable to the world). Banana boat has a reasonable track record and several of these available.