The first one is Strombus (Conomurex) luhuanus. It's a true conch, and will eat both micro- and macroalgae. It will spend part of the time buried, or partially buried, in the sand.
The second one is a Turbo species, but it's hard to tell for sure which one. All of them are algal grazers, though. It may be Turbo argyrostomus.
Cheers,
Don