The starfish are not suicidal, they are just SLOW.
Basically the tide was out to the lowest level that I have ever seen it, and the Starfish just can't move quickly enough to keep with the 'drift out'
The seagulls don't even like then that much .... they mess about with them, nibble a bit off, drop them on the prom and the pier... but they are more trouble than they are worth (especially if there are some mussels or ice cream in the vicinity)