  Marine animals and deep underwater objects are difficult to recognize and
monitor for safety of aquatic life. There is an increasing challenge when the
water is saline with granular particles and impurities. In such natural
adversarial environment, traditional approaches like CNN start to fail and are
expensive to compute. This project involves implementing and evaluating various
object detection models, including EfficientDet, YOLOv5, YOLOv8, and
Detectron2, on an existing annotated underwater dataset, called the
Brackish-Dataset. The dataset comprises annotated image sequences of fish,
crabs, starfish, and other aquatic animals captured in Limfjorden water with
limited visibility. The aim of this research project is to study the efficiency
of newer models on the same dataset and contrast them with the previous results
based on accuracy and inference time. Firstly, I compare the results of YOLOv3
(31.10% mean Average Precision (mAP)), YOLOv4 (83.72% mAP), YOLOv5 (97.6%),
YOLOv8 (98.20%), EfficientDet (98.56% mAP) and Detectron2 (95.20% mAP) on the
same dataset. Secondly, I provide a modified BiSkFPN mechanism (BiFPN neck with
skip connections) to perform complex feature fusion in adversarial noise which
makes modified EfficientDet robust to perturbations. Third, analyzed the effect
on accuracy of EfficientDet (98.63% mAP) and YOLOv5 by adversarial learning
(98.04% mAP). Last, I provide class activation map based explanations (CAM) for
the two models to promote Explainability in black box models. Overall, the
results indicate that modified EfficientDet achieved higher accuracy with
five-fold cross validation than the other models with 88.54% IoU of feature
maps.
