All snails have essentially the same body plan and all, marine and land alike, have two pairs of tentacles. They don't have true eyes; rather, they have light-sensitive eyespots. On land snails, these are at the tips of the longer tentacles; on marine snails, they're at the bases. The other tentacles are used for smell and touch. Not all marine snails breathe through siphons, only those that bury themselves and need to breathe while buried. The Jeweled Top Snail lives on kelp fronds and thus has no need of a siphon to draw water over its gills.