This poem left me with a cold feeling although honeymoons were mentioned. Strange huh?
The word "visitors" struck me the most. Maybe they're visiting some well-known house, a house-museum. It made me think of all us being just passerby in this life, that better leave others with not just "trinkets in a raw", but something significant.
"domesticity in fragments of a beach" sounds soulless, actually the feeling I had was provoked even before reading the poem, by its title, shells... seem so interesting and even beautiful, but everyone knows that there is nothing inside, especially in the ones that are
"trinkets in a row
along the mantelpiece,"

Domesticity is somewhere else - in the toys  out of the box and scattered around the floor; under the cover of the lunch box prepared by your wife in the morning...

Memories are alive until people who shared them are not here anymore, there is no need in tangible souvenirs, imo.

I like the fact that there is no beginning and no end:  it's reached by not using capital letters at all and no period in the end of the poem, it's like a scene that was captured by a photographer! Love it! All we have are two commas, that separate the first scene with the mantelpiece and the last one with visitors, the middle of the poem is captured by them, imprisoned.