Expelling from rocks

[fsas89]

I saw something squirt up from my rocks and looked, there’s something like a slug/snail type thing just continually “squirting” up. Any ideas what it is? Hope the video works.

 

[Fish Think Pink]

I saw something squirt up from my rocks and looked, there’s something like a slug/snail type thing just continually “squirting” up. Any ideas what it is? Hope the video works.

video downloaded but didn't play correctly for me maybe it is just my PC