Glowing?
There alot of small marble-like jellyfish in the surf right now that can cause the phosflorescence if he got caught up in it. Otherwise if it was within the creature, he could have been eaten something to cause the condition, like squid, jellyfish and other phosflorescence. Odd.
You'll find them in the gut of some big bass! I think many bass take small, bottom-bouncing bucks thinking they are these sand beggers and not a bait fish. I used to tie short hair -1oz banana heads with grey over white to match them. Had fish but was never as productive as other methods and never made a perminant spot in the arsenol.