What this on my glass?

[GaryE]

These are all over my glass. Any idea what they are?

 

[cloak]

Hydroids. These are relatively harmless and tend to disappear just as fast as they show up.

 

[GaryE]

Thanks

 

[Copingwithpods]

Possibly Hydromedusae, tiny hydroid jellyfish. Not really good but not bad either. They can sting stuff but usually all die off on their own.