Helmet Shell at Changi?

I was back at Changi again to catch the low tide before it ended. It was as crowded although it was raining heavily earlier this morning. The shore are packed with swimming, fishing and pick & choose activities.
Due to the rain earlier on, most of the animals had burrowed to stay away from the fresh water. Animals that do not burrow such as fan shells just like sitting duck - have to endure the fresh water and just waiting to be picked by predators (to me, human is their biggest predators).
This sea cucumber was half burrowed when I spotted it.
So as this Moon snail.This lump of seaweed looks like a sea cucumber when I found it near the sea grass bed.After a few wash... yes is a sea cucumber!and another Ball Sea CucumberThe little pink sea cucumbers are the only animals that can be found easily. They just attached to sea grass or anything that is not moving. This sea cucumber extending the tenticles to feed.I have no idea what shell is this but it do looks like a helmet shell.This is the only Striped hermit crab that I saw this morning.Saw this tiny Moons crab swimming from one place to another so I pick it up to take his photo. It dissapear immediately the minute I put it back to water. Moons crab with all leg flattened can swim faster than swimming crabs and burrow in lightning speed!This flower crab almost invisible when it stay motionless on the seagrass bed. There are a few anemones here and there but the colour show that they are not very healthy. Too much fresh water again?

Hundreds of Geographic sea hares that we saw on Friday are no way to be found. I wonder are all of them burrowed into the sands or they prefer to stay at the deeper water?