This is one of my favorite songs for solo singing for kindergarten and first grade:

Lamar Robertson and Ann Eisen have a different version in their book An American Methodology.  This version I learned from Sue Leithold-Bowcock.

Formation:  seated circle

Action:  as the song is sung, the students pass a sea shell around the circle.  Whoever has the seashell on the final "do" of the song ("sing about the sea")  holds onto the sea shell.  All players ask that player "What do you see?"  The student sings the answer "I see a whale," but they improvise something they would see at the sea or ocean for the word whale.  

I love that it's a simple solo singing exercise but also has a simple introduction to improvisation.   In addition to some traditional answers of seeing sharks, whales, eels, crabs, etc., I've had some pretty funny and clever answers to what my students see. Some of the more popular/silly ones include seeing Spongebob Square Pants and some other characters from his series.  Others include pirates, treasure chests, lifeguards, umbrellas and so forth.  But the all-time high chuckle answer is "bikini."  :)

Pedagogically, I use the song to reinforce "so-mi" in first grade.  A fun coincidence is that it starts "so mi so mi" just as the song "Snail Snail" does.  With my students we actually use seashells to write the so-mi pattern on the staff.  This year I did use it with my second graders and we wrote the entire solfa of the song on the staff using seashells.  This alleviated the rhythm writing, which they aren't able to do yet.  (I teach dotted eighth/sixteenth pattern in 5th grade)  And they really enjoyed using the seashells to write the song. :)

With kindergarten there is a really sweet finger play that can be used in conjunction with the Sea Shell song:

Five Little Seashells:

Five little seashells (hold out five fingers)

Lying on the shore.

Swish! (open your other hand and pass it over the five fingers)

Went the waves (make a light fist with the first hand and pass the open hand back over the first hand)

And then there were four (hold out four fingers on the first hand)

Four little seashells, pretty as can be.

Swish went the ways and then there were three.

Three little seashells, all pearly and new.

Swish went the waves and then there were two.

Two little seashells, lying in the sun.

Swish went the waves and then there was one.

One little seashell, lying all alone.

I whispered "shh!" and I took it home.

Some extensions include using scarves to act as the ocean waves on "swish!" and/or an ocean drum or rain stick to sound like the ocean waves.