What are Characteristics of good core samplers?

Perpendicular placement: The core sampler must make a vertical or straight entry into sediments to secure a reliably representative cross-section sample.
Penetration: It must penetrate the sediments you expect to find and adaptable for many field situations.
Core retention: There should be minimal loss of any part of the sample during return to the surface.
Maximum sample validity: This means:
a. Samplers intended for layered sediments should obtain cores showing minimum disturbance of layers by compression or by displacement around the circumference.
b. Samplers intended to obtain bottom sediments and their resident fauna need a design which causes minimum displacement or escape of fauna during sampling.
Simplicity: Purchase the simplest instrument capable of producing the type of samples you require.