Ship navigation through ice-infested waters is a problem of deep concern to the oil exploration industry of the northern countries. Conventional marine radars do not perform satisfactorily in detecting small targets such as small pieces of iceberg. This paper reports a new method for detection in an ocean environment. The approach is based on the recent observation that sea clutter, radar echoes from the sea surface, can be modeled as a nonlinear deterministic dynamical system as an alternative to the conventional stochastic process. Based on this model, detection in sea clutter may be considered as classification of dynamical systems instead of statistical hypothesis testing. Two dynamical detection methods are proposed. The first one uses a dynamical invariant called attractor dimension to distinguish a target and a pure clutter process. The second approach tries to detect the existence of a target by observing the `difference' of the motion of the target and the clutter process. To show the validity of the idea of dynamical detection in sea clutter, real sea clutter and target data were used in this study.