Jasper, its not a silly question but this might be a silly answer, lol. I dont know what it is, its out of the sea! it was about 8" long and yes it hard loads of legs, to tell the truth, it looked a horrible thing, like a big wood louse.
That's exactly what it is, Wood Louse you see running about on land under old logs etc. are actually crustaceans, they keep a bubble of water on their body and do not breathe in air the way insects do.
Their bigger ancestors still live in the sea. Which is what I believe RFYL has took a pic of.
Wow, thats fasinating, and are these things